Код в первом кадре. На сцене mc.

Код AS1/AS2:
stop();
onEnterFrame = onEnterFrameHandler;
mc.stop();
function onEnterFrameHandler():Void
{
var currentFrame:Number = Math.ceil(mc._totalframes * getBytesLoaded() / getBytesTotal());
if (currentFrame != mc._currentframe)
mc.gotoAndStop(currentFrame);
if (currentFrame == mc._totalframes)
delete this.onEnterFrame;
}