AS3, file load time measurement

I want to measure the time a file is loaded from a remote directory.
I wrote the code as below, but I don't trust it.
Please let me know if there are any problems and ask for better sample code.

function musicPlay(url: String): void {

	if (channel) { channel.stop(); }

	url = "http://....................mp3";
	sound = new Sound(new URLRequest(url));
	channel = new SoundChannel();

	sound.addEventListener(ProgressEvent.PROGRESS, progressHandler);
	sound.addEventListener(Event.COMPLETE, loadCompleteHandler);

	channel = sound.play(0);
}

var beginTime: Number = 0;
var endTime: Number = 0;	

function progressHandler(e: ProgressEvent): void {

	var aDate: Date = new Date();
	if (e.bytesLoaded == 0) {
		beginTime = aDate.valueOf();
	}
		
	if (e.bytesLoaded == e.bytesTotal) {
		var zDate: Date = new Date();
		endTime = zDate.valueOf();
	
		var passedTime: Number = (endTime-beginTime)/1000; 
		trace("Loaded Speed : " + passedTime + "/s");
	}
}

function loadCompleteHandler(e: Event): void {
	//...............................................
}