Fade-in sound effect without onEnterFrame event?

[legacye]

I have an audio player I made in Flash CS3 that runs off an XML Playlist.

I've been trying to add a fade-in effect to the mp3's that is triggered when the user clicks the play button but unfortunately, I've been running into a few problems...

I know that easiest way to code up the fade-in effect is using the this.onEnterFrame event, but due to the way my player's coded, I can't use this.

To make up for the event, I created two functions. The first is called when the user clicks on the play button:

function startFade()
{
	vols = 0;
	id = setInterval(volStep, 500);
}

function volStep(){
	
	if(stopfade==false)
	{
		
	step = 5;

	vols = vols + step;
	
	if(vols>=100)
	{ 
	     vols =100; 
	}
	
	_sound.setVolume(vols);

	}
	
	if(vols==100)
	{ 
	
			stopfade=true; 
			clearInterval(id);
			
	}
	updateAfterEvent();
	
}

Now, I've tested both these loops and the "vol" variable increments correctly the way it should. When I test out the value for _sound.getVolume() it's value is also correct after being updated..but for some reason...the actual sound levels for the object won't correspond to this (i.e I dont hear anything at all).

For reference sakes, I'm also including a snippet of where/how I'm using the above in my play button

                //redfine the object each time we change tracks
                _sound = new Sound(); 
		_sound.onSoundComplete = mp3.playNext;  

		
		var path = mp3.path;
		if (path.indexOf("://")<0) {
			path = _root.urlpath+path;
		}
	
		
		_sound.loadSound(path, true);
		
		startFade();

With the exception of the fade-in problems, everything else in the player works perfectly..

I'd love to get some help with this problem as I've tried over 5 or 6 different solutions from actionscript.org so far and neither have worked yet.