adding AS to timeline effect frames

[nausea]

What I'm trying to do, is to make a movie clip play when I rollOver a button. But, in the MC I have a timeline effect, fading in.
My problem is, that when I try and add stop() to the first and last frames of the MC, it just adds it to the whole thing. How can I add AS's to individual frames? Because I need the MC to stop at the last frame until I rollOut, what it does is it just goes back to the first frame and stops.
How do I get around this?

Thanks.

[Cota]

You should be using KEYFRAMES for that. Simply right click on the frame of choice and select Insert Keyframe, then add the code.