diff --git a/Classes/PHPExcel/Writer/Excel2007.php b/Classes/PHPExcel/Writer/Excel2007.php
index 3d67b3d..4e93201 100644
--- a/Classes/PHPExcel/Writer/Excel2007.php
+++ b/Classes/PHPExcel/Writer/Excel2007.php
@@ -35,6 +35,17 @@
  */
 class PHPExcel_Writer_Excel2007 extends PHPExcel_Writer_Abstract implements PHPExcel_Writer_IWriter
 {
+	/**
+	 * Pre-calculate formulas
+	 * Forces PHPExcel to recalculate all formulae in a workbook when saving, so that the pre-calculated values are
+	 *    immediately available to MS Excel or other office spreadsheet viewer when opening the file
+	 *
+     * Overrides the default TRUE for this specific writer for performance reasons
+     *
+	 * @var boolean
+	 */
+	protected $_preCalculateFormulas = FALSE;
+
 	/**
 	 * Office2003 compatibility
 	 *
diff --git a/Classes/PHPExcel/Writer/Excel2007/Workbook.php b/Classes/PHPExcel/Writer/Excel2007/Workbook.php
index db88e74..2abf9eb 100644
--- a/Classes/PHPExcel/Writer/Excel2007/Workbook.php
+++ b/Classes/PHPExcel/Writer/Excel2007/Workbook.php
@@ -194,10 +194,14 @@ class PHPExcel_Writer_Excel2007_Workbook extends PHPExcel_Writer_Excel2007_Write
 	{
 		$objWriter->startElement('calcPr');
 
-		$objWriter->writeAttribute('calcId', 			'124519');
+		//	Set the calcid to a higher value than Excel itself will use, otherwise Excel will always recalc
+        //  If MS Excel does do a recalc, then users opening a file in MS Excel will be prompted to save on exit
+        //     because the file has changed
+		$objWriter->writeAttribute('calcId', 			'999999');
 		$objWriter->writeAttribute('calcMode', 			'auto');
 		//	fullCalcOnLoad isn't needed if we've recalculating for the save
-		$objWriter->writeAttribute('fullCalcOnLoad', 	($recalcRequired) ? '0' : '1');
+		$objWriter->writeAttribute('calcCompleted', 	($recalcRequired) ? 1 : 0);
+		$objWriter->writeAttribute('fullCalcOnLoad', 	($recalcRequired) ? 0 : 1);
 
 		$objWriter->endElement();
 	}
diff --git a/Examples/03formulas.php b/Examples/03formulas.php
index 04e56d2..b493aa5 100644
--- a/Examples/03formulas.php
+++ b/Examples/03formulas.php
@@ -107,6 +107,15 @@ echo date('H:i:s') , " Write to Excel2007 format" , EOL;
 $callStartTime = microtime(true);
 
 $objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
+
+//
+//  If we set Pre Calculated Formulas to true then PHPExcel will calculate all formulae in the
+//    workbook before saving. This adds time and memory overhead, and can cause some problems with formulae
+//    using functions or features (such as array formulae) that aren't yet supported by the calculation engine
+//  If the value is false (the default) for the Excel2007 Writer, then MS Excel (or the application used to
+//    open the file) will need to recalculate values itself to guarantee that the correct results are available.
+//
+//$objWriter->setPreCalculateFormulas(true);
 $objWriter->save(str_replace('.php', '.xlsx', __FILE__));
 $callEndTime = microtime(true);
 $callTime = $callEndTime - $callStartTime;
diff --git a/Examples/13calculation.php b/Examples/13calculation.php
index c1c0de8..a8f17b0 100644
--- a/Examples/13calculation.php
+++ b/Examples/13calculation.php
@@ -207,6 +207,15 @@ echo date('H:i:s') , " Write to Excel2007 format" , EOL;
 $callStartTime = microtime(true);
 
 $objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
+
+//
+//  If we set Pre Calculated Formulas to true then PHPExcel will calculate all formulae in the
+//    workbook before saving. This adds time and memory overhead, and can cause some problems with formulae
+//    using functions or features (such as array formulae) that aren't yet supported by the calculation engine
+//  If the value is false (the default) for the Excel2007 Writer, then MS Excel (or the application used to
+//    open the file) will need to recalculate values itself to guarantee that the correct results are available.
+//
+//$objWriter->setPreCalculateFormulas(true);
 $objWriter->save(str_replace('.php', '.xlsx', __FILE__));
 $callEndTime = microtime(true);
 $callTime = $callEndTime - $callStartTime;
diff --git a/changelog.txt b/changelog.txt
index cbbc50f..3eca4dc 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -33,6 +33,10 @@ Fixed in develop branch for release v1.8.0:
 - Feature:  (MBaker)                     - Added Horizontal FILL alignment for Excel5 and Excel2007 Readers/Writers, and Horizontal DISTRIBUTED alignment for Excel2007 Reader/Writer
 - General:  (cdhutch)   Work item 20055  - Remove array_shift in ReferenceHelper::insertNewBefore improves column or row delete speed
 - General:  (MBaker)                     - Improve stock chart handling and rendering, with help from Swashata Ghosh
+- General:  (MBaker)                     - Fix to calculation properties for Excel2007 so that the opening application will only recalculate on load
+                                             if it's actually required
+- General:  (MBaker)                     - Modified Excel2007 Writer to default preCalculateFormulas to false
+                                           Note that autosize columns will still recalculate affected formulae internally
 
 
 Fixed in develop branch for release v1.7.9: