Sum column DataGrid

Hello,

Personally I have a DataGrid, and this data grid contains some fields, I would like to modify or enter a value in column "Quantity2" I automatically calculate Quantity2 + Price column and return the value in column "Result" how could I make it friends?

<?xml version="1.0"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" 
   initialize="initData()">
   <mx:Script>
   <![CDATA[
   	import mx.controls.Alert;
      import mx.collections.*;
      private var DGArray:Array = [
         {Artist:'Pavement', Album:'Slanted and Enchanted', Price:10},
         {Artist:'Pavement', Album:'Brighten the Corners', Price:20}];
         
      [Bindable]
      public var initDG:ArrayCollection;
      public function initData():void {
         initDG=new ArrayCollection(DGArray);
      }
      
      
      
      
   ]]>
   </mx:Script>

   <mx:DataGrid id="myGrid" width="350" height="200"  dataProvider="{initDG}" editable="true" >
      <mx:columns>
         <mx:DataGridColumn dataField="Album"  editable="false" />
         <mx:DataGridColumn dataField="Price"  editable="false" />
         <mx:DataGridColumn dataField="Quantity2"  editable="true"/>
         <mx:DataGridColumn dataField="Result"  editable="false" />
      </mx:columns> 
   </mx:DataGrid>
</mx:Application>

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