either way it should really matter...no?

I mean 30% of any number is still 30%...

example:
Code:
if (targetContainer.getBytesLoaded() > 0) {
	var percent = Math.round((100 / targetContainer.getBytesTotal()) * targetContainer.getBytesLoaded());
	if(percent == 30){
		//start playing
	}
} else {
	var percent = 0;
}
or really just:
Code:
var percent = Math.round((100 / targetContainer.getBytesTotal()) * targetContainer.getBytesLoaded());
if(percent == 30){
	//start playing
}
Im not sure how your using your 'check'...but the code is an example