Referencing a movie clip within a button?

1

i have a button that has a movie clip in it. I would like to play the movieClip on the rollOver event, but I can’t get it to play. Here is what I hae got

on(rollOver) {
_root.myProjects_btn.folderZoom_mc.gotoAndPlay(“start”);
}

I have also tried but it didn’t work either

on(rollOver) {
this.folderZoom_mc.gotoAndPlay(“start”);
}

Thanks for the help