Ans:

The following example will be helpful for you please try it.

main.mxml

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" 
width="300" height="150"
layout="absolute" 
creationComplete="init()">
  <mx:Script>
   <![CDATA[
     import mx.collections.ArrayCollection;

     [Bindable]
     private var items:ArrayCollection;

     private function init():void
     {
       items = new ArrayCollection();
       items.addItem(new NameItem("A", true));
       items.addItem(new NameItem("B", false));
       items.addItem(new NameItem("C", false));
       items.addItem(new NameItem("D", true));
       items.addItem(new NameItem("E", false));
     }
   ]]>
 </mx:Script>
<mx:DataGrid dataProvider="{items}" 
  editable="true" width="100%" height="100%">
    <mx:columns>
        <mx:DataGridColumn headerText="Name" 
         dataField="name" editable="false" />
        <mx:DataGridColumn headerText="Access" 
           dataField="access"
           itemEditor="ComboEditor" 
           editorDataField="newValue" width="125"/>
    </mx:columns>
  </mx:DataGrid>
</mx:Application>

The NameItem class is following

package
{
  [Bindable]
  public class NameItem
  {
    public var name:String;
    public var access:Boolean;

    public function SimpleItem(name:String, access:Boolean)
    {
      this.name = name;
      this.access = access;
    }
  }
}

ComboEditor.mxml as an itemrenderer

<?xml version="1.0" encoding="utf-8"?>
<mx:Box xmlns:mx="http://www.adobe.com/2006/mxml" 
width="100%" height="100%" horizontalAlign="center">
  <mx:Script>
   <![CDATA[
     override public function set data(value:Object):void
     {
       super.data = value;
       newValue = value.access;
     }
   ]]>
 </mx:Script>
  <mx:Boolean id="newValue" />
  <mx:ComboBox id="comboItem" selectedIndex="{data.access ? 0 : 1}"
     change="{newValue = (comboItem.selectedIndex == 0)}">
    <mx:dataProvider>
      <mx:Array>
        <mx:String>Yes</mx:String>
        <mx:String>No</mx:String>
      </mx:Array>
    </mx:dataProvider>
  </mx:ComboBox>
</mx:Box>