I'm using AS2...
Ok so on the main timeline I have two movieclips. One is called exitBtn and one is called back_mc. Then, there is a mc inside of back_mc that's called cta.

I want the cta movieclip to play an animation on a frame labeled "rollOver" when the user rolls over the mc exitBtn.

This is what I currently have on the main timeline (which isn't working)...

Actionscript Code:
exitBtn.on(rollOver){
    back_mc.cta.gotoAndPlay("rollOver");
}