DataGridColumn editable false?

Question

how to dinamically make editable false for datagridColumn ?
my code is like that
<mx:DataGridColumn
dataField="dispatch" 
headerText="Dispatch"
resizable="false"
sortable="false"
editorDataField="selected"
rendererIsEditor="true"
itemRenderer="mx.controls.CheckBox"
>
</mx:DataGridColumn>
when I always try to set editable false for column.but it never became as I need.Any Ideas?

Answer 1

here is the sample
<?xml version="1.0" encoding="utf-8"?>
<!--Project :UserLevel~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-->
<!--File     :TestGrid.mxml~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-->
<!--Date    :Mar 24, 2011~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-->
<!--Author     :Administrator~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-->
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="955" minHeight="600">
<fx:Script>
<![CDATA[
import mx.collections.ArrayCollection;
[Bindable]
private var acDao:ArrayCollection=new ArrayCollection();
protected function button1_clickHandler(event:MouseEvent):void
acDao.addItem({col1:1,col2:2,col3:true});
acDao.addItem({col1:11,col2:22,col3:false});
acDao.addItem({col1:12,col2:23,col3:true});
acDao.addItem({col1:13,col2:24,col3:false});
protected function button2_clickHandler(event:MouseEvent):void
for each(var temp:Object in dgDao.dataProvider as ArrayCollection)
trace("first :"+temp["col1"]+"second :"+temp["col2"]+"third :"+temp["col3"]);
]]>
</fx:Script>
<fx:Declarations>
<!-- Place non-visual elements (e.g., services, value objects) here -->
</fx:Declarations>  
<!--Visual Components Here~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-->   
<mx:DataGrid x="300" y="194" id="dgDao" dataProvider="{acDao}" editable="true">
<mx:columns>
<mx:DataGridColumn headerText="Column 1" dataField="col1"/>
<mx:DataGridColumn headerText="Column 2" dataField="col2"/>
<mx:DataGridColumn headerText="CheckBox" dataField="col3" editable="true" itemRenderer="mx.controls.CheckBox" editorDataField="selected" rendererIsEditor="true"/>
</mx:columns>
</mx:DataGrid>
<s:Button x="300" y="150" label="Load" click="button1_clickHandler(event)"/>
<s:Button x="383" y="150" label="view" click="button2_clickHandler(event)"/>
</s:Application>
How can I make the checkbox column editable false dinamically?