Advanced button? rollover?

Hello, my problem is this, I want to have an expanding and collapsing button. When the user rolls over the button it plays forward and gets bigger when the user rolls off the button it should return to its original size from the point that the user rolled off.

If you click on this attached button then rollover youll see what i mean (sort of) the problem is if you roll on and off quickly it wont work because it doesnt return from every point.

Basically if flash could somehow play the framehead backwards this would be ideal. Alternavely I have to work out what frame its on when the user rolls off and tell my movie to play a certain frame according to this. I tried to use _framesloaded but this was difficult…

does anybody know what im talking about - does anybody know how to achieve what im after?

thanks…