Resize loadClip image

Some images I load dynamically are too big so I would like to scale them to fit the stage.

var imgCont:MovieClip = _root.mcHolder;

var mcLoader:MovieClipLoader = new MovieClipLoader();

var mcListener:Object = new Object;



mcListener.onLoadComplete = function(){

this returns 0.
Why does it return 0 when the image loaded is obviously much larger then 0 pixels.

How do I change the width and height of imgCont to a specified dimension.