TweenEvent.MOTION_FINISH problems

programming flash
1

Im having problems with the Motion finish tween event, whenever I try to use it I just get an error saying 1046: Type was not found or was not a compile-time constant: TweenEvent.
Ive seen examples using the same structure as Im using, I cant figure out why mine isnt working, am I doing something daft here?

Heres my code

cover1.addEventListener(MouseEvent.CLICK, zoom);
function zoom(event:MouseEvent) {
	import fl.transitions.Tween;
	import fl.transitions.easing.*;
	var Xscale:Number = cover1.scaleX*0.6;
	var Yscale:Number = cover1.scaleY*0.6;
	var myTweenX:Tween = new Tween(cover1, "scaleX", Regular.easeOut, cover1.scaleX, Xscale, 10);
	var myTweenY:Tween = new Tween(cover1, "scaleY", Regular.easeOut, cover1.scaleY, Yscale, 10);
	myTweenY.addEventListener(TweenEvent.MOTION_FINISH, advanceFrame);
}
function advanceFrame (e:TweenEvent) {
	trace("hello");
}

Thanks