onEnterFrame simple action

[fangaas]

Hi guys, a simple question that has been bugging me.

I have a movie clip on the main timeline and I want to make it so that I can control the clip from the timeline with an onEnterFrame action.

I tried assigning:

this.onEnterFrame = function(){
_root.mymc.gotoAndPlay(10);
}

To a frame on the main timeline but to no effect. How can I get this to work?
Need help asap, thanks ;D