Flash CS3 Play/Stop audio button problem

[COLOR=#000000][FONT=verdana]I made a play/stop audio button with this youtube tutorial (youtube.com/watch?v=XU6oMEFUFF8) but after the sound is finished I want the play button to show up agian.[/FONT][/COLOR]

[COLOR=#000000][FONT=verdana]Here is the actionscript:[/FONT][/COLOR]

[COLOR=#000000][FONT=verdana]import flash.events.MouseEvent;[/FONT][/COLOR]

[COLOR=#000000][FONT=verdana]play_btn.addEventListener(MouseEvent.CLICK,clickha ndler);[/FONT][/COLOR]
[COLOR=#000000][FONT=verdana]stop_btn.addEventListener(MouseEvent.CLICK,clickha ndler);[/FONT][/COLOR]
[COLOR=#000000][FONT=verdana]function clickhandler(event:MouseEvent):void{[/FONT][/COLOR]
[COLOR=#000000][FONT=verdana]swapChildren(play_btn,stop_btn);[/FONT][/COLOR]
[COLOR=#000000][FONT=verdana]}[/FONT][/COLOR]

[COLOR=#000000][FONT=verdana]what code should I add to my current code?[/FONT][/COLOR]

[COLOR=#000000][FONT=verdana]I also can send you the Fla.[/FONT][/COLOR]