Disabling individual buttons on a Flex ButtonBar control

<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/01/10/disabling-individual-buttons-on-a-flex-buttonbar-control/ -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">
 
    <mx:Style>
        ButtonBar {
            buttonStyleName: myCustomButtonStyleName;
        }
 
        .myCustomButtonStyleName {
            cornerRadius: 0;
        }
    </mx:Style>
 
    <mx:Script>
        <![CDATA[
            import mx.controls.buttonBarClasses.ButtonBarButton;
 
            private function toggleButton(idx:uint, selected:Boolean):void {
                var b3:ButtonBarButton = buttonBar.getChildAt(idx) as ButtonBarButton;
                b3.enabled = selected;
            }
        ]]>
    </mx:Script>
 
    <mx:Array id="arr">
        <mx:Object label="Button" />
        <mx:Object label="ButtonBar" />
        <mx:Object label="ColorPicker" />
        <mx:Object label="ComboBox" />
    </mx:Array>
 
    <mx:ApplicationControlBar dock="true">
        <mx:Form styleName="plain">
            <mx:FormItem label="Button enabled:">
                <mx:CheckBox id="ch1"
                        selected="true"
                        click="toggleButton(0, ch1.selected);" />
            </mx:FormItem>
            <mx:FormItem label="ButtonBar enabled:">
                <mx:CheckBox id="ch2"
                        selected="true"
                        click="toggleButton(1, ch2.selected);" />
            </mx:FormItem>
            <mx:FormItem label="ColorPicker enabled:">
                <mx:CheckBox id="ch3"
                        selected="true"
                        click="toggleButton(2, ch3.selected);" />
            </mx:FormItem>
            <mx:FormItem label="ComboBox enabled:">
                <mx:CheckBox id="ch4"
                        selected="true"
                        click="toggleButton(3, ch4.selected);" />
            </mx:FormItem>
        </mx:Form>
    </mx:ApplicationControlBar>
 
    <mx:ButtonBar id="buttonBar"
            dataProvider="{arr}"
            itemClick="lbl.text = event.label;" />
 
    <mx:Label id="lbl" />
 
</mx:Application>