How to edit cell in a Data Grid

Question

Hai
    I have pasted the mxml below.
   I need how to edit a cell in a datagrid.
  1. Run the mxml, enter the values in the textbox and click add button.
  2. then click AND button, now u can see the values displayed in the grid.
3. Then again change the second combobox and enter the values in the textbox and click add
4. Now i need to edit the values for a particular cell in the datagrid.
In the below code u can see the Value column,
i need to edit oly that cell of a particular row .
Can anyone help me.
Thanks in Advance
<?xml version="1.0" encoding="utf-8"?><mx:Application 
xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
<mx:Script>
<![CDATA[
// ActionScript fileimport  
mx.rpc.events.FaultEvent;
import  
mx.controls.Alert; 
import mx.managers.CursorManager;
import  
mx.collections.ArrayCollection;[
Bindable] 
public var adhoc:ArrayCollection = new ArrayCollection();[
Bindable] 
public var serverString = "" ; 
private function initImage(event:MouseEvent):void { 
if(adhoc.length > 0){CursorManager.setBusyCursor();
private function onChange():void{ 
if(comboBox.selectedIndex == 0){ 
else{ 
private function onChange1():void{ 
if(combo2.selectedItem == "DATEDEPLOYED" || combo2.selectedItem == "DATEUPLOADED"){datepick.visible =
truetxt.visible =
false}
else{txt.visible =
truedatepick.visible =
false}
private function add():void

Answer 1

You can enable editing in a DG to the whole DG or only to certain columns
http://blog.flexexamples.com/2008/05/11/creating-an-editable-datagrid-control-in-flex/
If you want to enable editing to a very specific cell then you use the event itemEditBegin to prevent editing a cell that doesn't meet your criteria
http://livedocs.adobe.com/flex/3/html/help.html?content=celleditor_7.html