Interactive Image Panning within a Mask

Hey guys thanks for the help so far. The last piece to the puzzle for me is figuring out how to scroll a movie clip within a mask. I’m currently working with the script taken from the Interactive Image Panning tutorial on this site as a base. Right now the script references the entire Stage area for scrolling the image whereas I want this to happen just within a mask. How do I set this up. Here is where I have the script right now:

this.onMouseMove 	= function() 	{ constrainedMove(Work_placeholder, 		4, 1); 		}; function  	constrainedMove(target:MovieClip, 	speed:Number, 	dir:Number) 	{ var mousePercent:Number 		= _xmouse/Stage.height; 		var mSpeed:Number; 		if (dir 		== 1) 		{ mSpeed = 			1-mousePercent; 			} else 		{ mSpeed = 			mousePercent; } target.destY 		= Math.round(-((target._height-Stage.height)*mSpeed)); 		target.onEnterFrame 		= function() 		{ if (target._y 			== target.destY) 			{ delete  				target.onEnterFrame; } else 			{ target._y 				+= Math.ceil((target.destY-target._y)*(speed/100));}}; }

ps. the instance name of my mask is Work_mask (movie clip)