diff --git a/app/Controllers/Api/EntryApiController.php b/app/Controllers/Api/EntryApiController.php
index a8d56c5..d17d358 100644
--- a/app/Controllers/Api/EntryApiController.php
+++ b/app/Controllers/Api/EntryApiController.php
@@ -88,26 +88,102 @@ class EntryApiController extends BaseController
         
         try {
             $controlId = $input['controlId'] ?? 0;
-            $testId = $input['testId'] ?? 0;
-            $dates = $input['dates'] ?? '';
-            $resvalues = $input['resvalue'] ?? [];
+            $yearMonth = $input['yearMonth'] ?? '';
+            $operation = $input['operation'] ?? 'replace';
+            $tests = $input['tests'] ?? [];
+            $results = [];
+            $statistics = [];
+            $validations = [];
 
-            foreach ($resvalues as $day => $value) {
-                if (!empty($value)) {
-                    $resultData = [
-                        'control_ref_id' => $controlId,
-                        'test_ref_id' => $testId,
-                        'resdate' => $dates . '-' . str_pad($day, 2, '0', STR_PAD_LEFT),
-                        'resvalue' => $value,
-                        'rescomment' => '',
-                    ];
-                    $this->resultModel->saveResult($resultData);
+            foreach ($tests as $testData) {
+                $testId = $testData['testId'] ?? 0;
+                $resvalues = $testData['resvalue'] ?? [];
+
+                $controlTest = $this->controlTestModel->getByControlAndTest($controlId, $testId);
+                $mean = $controlTest['mean'] ?? 0;
+                $sd = $controlTest['sd'] ?? 0;
+                $sdLimit = $sd > 0 ? $sd * 2 : 0;
+
+                $testValues = [];
+                $validCount = 0;
+                $validSum = 0;
+                $validSqSum = 0;
+
+                foreach ($resvalues as $day => $value) {
+                    if (!empty($value)) {
+                        $resultData = [
+                            'control_ref_id' => $controlId,
+                            'test_ref_id' => $testId,
+                            'resdate' => $yearMonth . '-' . str_pad($day, 2, '0', STR_PAD_LEFT),
+                            'resvalue' => $value,
+                            'rescomment' => '',
+                        ];
+
+                        if ($operation === 'replace') {
+                            $this->resultModel->saveResult($resultData);
+                        } else {
+                            $existing = $this->resultModel->checkExisting($controlId, $testId, $resultData['resdate']);
+                            if (!$existing) {
+                                $this->resultModel->saveResult($resultData);
+                            }
+                        }
+
+                        $numValue = (float) $value;
+                        $testValues[] = $numValue;
+                        $validCount++;
+                        $validSum += $numValue;
+                        $validSqSum += $numValue * $numValue;
+
+                        $withinLimit = true;
+                        if ($sdLimit > 0) {
+                            $withinLimit = abs($numValue - $mean) <= $sdLimit;
+                        }
+
+                        if (!$withinLimit) {
+                            $validations[] = [
+                                'testId' => $testId,
+                                'day' => $day,
+                                'value' => $value,
+                                'mean' => $mean,
+                                'sd' => $sd,
+                                'status' => 'out_of_range'
+                            ];
+                        }
+                    }
                 }
+
+                if ($validCount > 0) {
+                    $calcMean = $validSum / $validCount;
+                    $calcSd = 0;
+                    if ($validCount > 1) {
+                        $variance = ($validSqSum - ($validSum * $validSum) / $validCount) / ($validCount - 1);
+                        $calcSd = $variance > 0 ? sqrt($variance) : 0;
+                    }
+                    $cv = $calcMean > 0 ? ($calcSd / $calcMean) * 100 : 0;
+
+                    $statistics[] = [
+                        'testId' => $testId,
+                        'n' => $validCount,
+                        'mean' => round($calcMean, 3),
+                        'sd' => round($calcSd, 3),
+                        'cv' => round($cv, 2)
+                    ];
+                }
+
+                $results[] = [
+                    'testId' => $testId,
+                    'saved' => count($resvalues)
+                ];
             }
 
             return $this->respond([
                 'status' => 'success',
-                'message' => 'save success'
+                'message' => 'save success',
+                'data' => [
+                    'results' => $results,
+                    'statistics' => $statistics,
+                    'validations' => $validations
+                ]
             ]);
         } catch (\Exception $e) {
             return $this->failServerError('Something went wrong: ' . $e->getMessage());
diff --git a/app/Models/ResultModel.php b/app/Models/ResultModel.php
index 9cc6a7e..9bb70a9 100644
--- a/app/Models/ResultModel.php
+++ b/app/Models/ResultModel.php
@@ -58,4 +58,15 @@ class ResultModel extends BaseModel
             return $builder->insert($data);
         }
     }
+
+    public function checkExisting($controlId, $testId, $resdate)
+    {
+        $builder = $this->db->table('results');
+        return $builder->select('result_id')
+                       ->where('control_ref_id', $controlId)
+                       ->where('test_ref_id', $testId)
+                       ->where('resdate', $resdate)
+                       ->get()
+                       ->getRowArray();
+    }
 }
diff --git a/app/Views/entry/monthly.php b/app/Views/entry/monthly.php
index 03f7e0f..c42cafa 100644
--- a/app/Views/entry/monthly.php
+++ b/app/Views/entry/monthly.php
@@ -133,8 +133,15 @@
                         <label class="block text-sm font-medium text-slate-700 mb-1">Monthly Comment</label>
                         <textarea x-model="comment" rows="2" class="w-full px-4 py-2.5 text-sm bg-slate-50 border border-slate-200 rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500/20 focus:border-blue-500" placeholder="Optional monthly comment"></textarea>
                     </div>
-                    <div class="flex items-end">
-                        <button @click="saveData()" data-save-btn :disabled="loading || selectedTests.length === 0" class="btn btn-primary w-full md:w-auto">
+                    <div class="flex items-end gap-3">
+                        <div class="flex-1">
+                            <label class="block text-sm font-medium text-slate-700 mb-1">Operation Mode</label>
+                            <select x-model="operation" class="w-full px-4 py-2.5 text-sm bg-slate-50 border border-slate-200 rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500/20 focus:border-blue-500">
+                                <option value="replace">Replace All</option>
+                                <option value="add">Add Only (Skip Existing)</option>
+                            </select>
+                        </div>
+                        <button @click="saveData()" data-save-btn :disabled="loading || selectedTests.length === 0" class="btn btn-primary flex-shrink-0">
                             <template x-if="!loading">
                                 <span class="flex items-center justify-center">
                                     <i class="fa-solid fa-check mr-2"></i>
@@ -182,6 +189,8 @@ document.addEventListener('alpine:init', () => {
         monthlyData: {},
         comment: '',
         dirtyCells: new Set(),
+        operation: 'replace',
+        saveResult: null,
 
         init() {
             this.loadDraft();
@@ -339,43 +348,61 @@ document.addEventListener('alpine:init', () => {
 
             this.loading = true;
             this.error = '';
+            this.saveResult = null;
             
             try {
+                const tests = [];
                 for (const testId of this.selectedTests) {
-                    const formData = new FormData();
-                    formData.append('controlid', this.control);
-                    formData.append('testid', testId);
-                    formData.append('dates', this.date);
-
+                    const resvalue = {};
                     let hasData = false;
                     for (let day = 1; day <= this.daysInMonth; day++) {
                         const key = testId + '_' + day;
                         const value = this.monthlyData[key];
                         if (value !== undefined && value !== null && value !== '') {
-                            formData.append(`resvalue[${day}]`, value);
+                            resvalue[day] = value;
                             hasData = true;
                         }
                     }
-
                     if (hasData) {
-                        const response = await fetch(`${window.BASEURL}/api/entry/monthly`, {
-                            method: 'POST',
-                            body: formData
-                        });
-                        const data = await response.json();
-                        if (data.status !== 'success') {
-                            throw new Error(data.message || 'Failed to save data for test ' + this.getTestName(testId));
-                        }
+                        tests.push({ testId, resvalue });
                     }
                 }
 
-                if (this.comment) {
-                    await this.saveComment();
-                }
+                const response = await fetch(`${window.BASEURL}/api/entry/monthly`, {
+                    method: 'POST',
+                    headers: { 'Content-Type': 'application/json' },
+                    body: JSON.stringify({
+                        controlId: this.control,
+                        yearMonth: this.date,
+                        operation: this.operation,
+                        tests: tests
+                    })
+                });
 
-                App.showToast('Data saved successfully!');
-                this.dirtyCells.clear();
-                this.saveDraft();
+                const data = await response.json();
+                
+                if (data.status === 'success') {
+                    this.saveResult = data.data;
+                    
+                    let message = 'Data saved successfully!';
+                    if (data.data.statistics && data.data.statistics.length > 0) {
+                        message += `\n\nStatistics:\n`;
+                        for (const stat of data.data.statistics) {
+                            const testName = this.getTestName(stat.testId);
+                            message += `${testName}: n=${stat.n}, Mean=${stat.mean}, SD=${stat.sd}, CV=${stat.cv}%\n`;
+                        }
+                    }
+                    
+                    if (data.data.validations && data.data.validations.length > 0) {
+                        message += `\n⚠️ ${data.data.validations.length} value(s) out of control limits!`;
+                    }
+                    
+                    App.showToast(message, 'success');
+                    this.dirtyCells.clear();
+                    this.saveDraft();
+                } else {
+                    throw new Error(data.message || 'Failed to save data');
+                }
             } catch (error) {
                 console.error(error);
                 this.error = error.message || 'Network error. Please try again.';