<?xml version="1.0"?>
<s:ComboBox xmlns:fx="http://ns.adobe.com/mxml/2009"
    xmlns:s="library://ns.adobe.com/flex/spark"
    xmlns:mx="library://ns.adobe.com/flex/mx">

    <fx:Script>
        <![CDATA[
            [Bindable]
            private var buttonLabel:String = "Click me!";
            private var clicks:int = 0;

            function button_clicked():void {
                clicks++;
                buttonLabel = clicks.toString();
            }
        ]]>
    </fx:Script>

    <s:Button id="button"
              label="{buttonLabel}"
              click="{button_clicked()}" />
</s:ComboBox>