yah, I use the same one as tomson, although I usually have some sort of bar on the screen showing the percentage, for this example we'll pretend that our loading bar on the screen is 255 pixels long... and I'm a code centralization whore so..... it would look like:
loader.onEnterFrame = function(){
loaded = getBytesLoaded();
total = getBytesTotal();
percent = (loaded/total)*100;
loader._width = (percent*2.55);
if (percent >=100){
gotoAndPlay("content");
}
}