you cant dynamically change the framerate but can have the same effect by using setInterval. for e.g suppose you have a box called mcBox. Then put a stop action in the first frame of the mcBox. The following will then move through its frames at a speed of 48 frames a sec
Code:
var nFramerate:Number = 48;
var nFrame:Number = setInterval(mover, 1000/nFramerate);
function mover():Void{
mcBox.nextFrame();
updateAfterEvent();
if(mcBox._totalframes == mcBox._currentframe){
clearInterval(nFrame);
trace("clear");
}
}