Make maxFontSize and minFontSize properties that you defined as variables usable
<?xml version="1.0"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"> <mx:Script> [Bindable] public var maxFontSize:Number = 15; [Bindable] public var minFontSize:Number = 5; </mx:Script> <mx:Text text="{maxFontSize}" /> <mx:Text text="{minFontSize}" /> <mx:Button click="maxFontSize=20; minFontSize=10;" /> </mx:Application>