getTimer

getTimer() //this will return the value of how long the movie has been playing

//// this is how you could wait before something starts //////
timeOut = getTimer()+5000; // find time movie's been playing and add 5 seconds to it

movieclip_mc.onEnterFrame = function(){
if(getTimer() > timeOut){ // if time playing is greater than timeOut variable
// do whatever you need here
delete(this.onEnterFrame); //delete the brain
}
}