[flexcoders] Enable / Disable Flex Menu Items Programmatically using AS 3.0

[bc24fl]

I have the following XML data defined in my app:

=========
<!-- Define the menu data. -->
    <mx:XML format="e4x" id="myMenuData">
        <root>
            <menuitem id="menuDrill" label="Drill =>" >
                <menuitem id="menuDown" label="Down" toggled="false"
enabled="true"/>
                <menuitem id="menuUp" label="Up" toggled="false"
enabled="true"/>
            </menuitem>
            <menuitem type="separator"/>
            <menuitem label="Lock / Unlock" type="check" toggled="false"/>
            <menuitem type="separator"/>   
            <menuitem label="Reset Graph" toggled="false"/>  
        </root>
    </mx:XML>
===========

I can statically disable one of the items by setting enabled="false",
however I need to disable the item by using Action Script 3.0.  

I've tried using dataDescriptor like so but it does not work:

===========
myMenu.dataDescriptor.setEnabled(myMenuData.menuDrill.menuDown,false);
===========

I've posted this on a few forums and haven't received a solution.  I
hope I can find one here.

Any help would be much appreciated.

Thanks.