as2 help with scrollbar - please!

[obli7vion]

I am having a very difficult time trying to make this scroll bar work. I am not math-minded, and I have been doing a lot of trial & error coding below. Sorry for the bad code.

An xml playlist item name is attached to the songbutton. The main issue I am having is that the list continues to scroll past the actual list items. How do I tell it to stop once it gets to the bottom of the list? Please let me know what other information I need to give in order to get help with this coding.

Thank you!

if(playlist._height <= playlist.itemsmask._height){
	scroller_mc.slider_mc._visible = false;
}
else{
	scroller_mc.visible = true;
}

scroller_mc.slider_mc.slider.onPress = function(){
	scrolling = true;
	
	this._parent.startDrag(0, this._parent._x, this._parent._parent.scrollBg_mc._y,
	this._parent._x, this._parent._parent.scrollBg_mc._y + this._parent._parent.scrollBg_mc._height);
}
scroller_mc.slider_mc.slider.onRelease = function(){
	scrolling = false;
	this._parent.stopDrag();
}

scroller_mc.slider_mc.slider.onReleaseOutside = function(){
	scrolling = false;
	this._parent.stopDrag();
}
	//controls the scrolling of the playlist
	if(scrolling == true){
		if(playlist.songbuttons._height > playlist.itemsmask._height){
			
			percentScroll = (scroller_mc.slider_mc._y/(scroller_mc.scrollBg_mc._y + scroller_mc.scrollBg_mc._height));
			
		
			
			playlist.songbuttons._y = (playlist.itemsmask._y - (playlist.songbuttons._height - playlist.itemsmask._height) * percentScroll) - 10;
			
		}
		
	}