<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="horizontal"
    creationComplete="creationCompleteHandler()">
<mx:Script>
<![CDATA[
    import mx.events.PropertyChangeEvent;

    [Bindable] private var bVar:uint = 0;
    [Bindable] private var btnLabel:String = "";

    private function creationCompleteHandler():void
    {
        addEventListener(PropertyChangeEvent.PROPERTY_CHANGE, propertyChangedHandler);
    }

    private function propertyChangedHandler(event:PropertyChangeEvent):void
    {
        if(event.property == "bVar")
            invalidateProperties();
    }

    override protected function commitProperties():void
    {
        super.commitProperties();
        btnLabel = bVar.toString();
    }
]]>
</mx:Script>
<mx:Button click="bVar++" label="{btnLabel}"/>
</mx:Application>