33% Preload

I’m using this to preload a movie that has a lot of images in it:

if (_root.getBytesLoaded()==_root.getBytesTotal()) {
gotoAndPlay(3); // or wherever the content starts
}
else {
gotoAndPlay(1); // restart the preloading cycle
}

Instead of checking to see if the movie is completely 100% loaded, I’d like to check to see if at least 33% is loaded and then start playing the movie while the rest downloads. Is this possible?