Add Button control as the first child of an HBox container
<?xml version="1.0"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"> <mx:states> <mx:State name="NewButton"> <mx:AddChild relativeTo="{h1}" position="firstChild"> <mx:Button id="buttonNew" label="New Button" /> </mx:AddChild> </mx:State> </mx:states> <mx:HBox id="h1"> <mx:Button label="Change State" click="currentState = currentState=='NewButton' ? '':'NewButton';" /> </mx:HBox> </mx:Application>