setMask problem

programming flash
1

Hi Guys,
Im trying to do this transition effect and been working on it for a while now.

I have a movie clip imageMC with a clipMC inside it where an external image is loaded into it. The movieClip is duplicted then resizes and fades out using the following code:

function loadImage(pic){
 
 pos=pos+1;
 var clip=imageMC.duplicateMovieClip("cont"+pos, this.getNextHighestDepth());
 curIm.setMask(maskMC);
 clip.swapDepths(curIm);
 curImage.scaleIt(); 
 
 curImage=clip.clipMC;
 curIm=clip;
 
 curImage.loadMovie(pic);
 curImage._x=-maskMC._width/2;
 curImage._y=-maskMC._height/2;
 clip.setMask(maskMC);
}

MovieClip.prototype.scaleIt = function() {
 //trace(this);
 var speed = 2;
 var spacing=0;
 var duration = 10;
 var step = 100/duration;
 this._alpha = 100;
 this.setMask(maskMC);
 this.onEnterFrame =function(){
  //this.setMask(maskMC);
  this._x = -this._width/speed;
  this._y = -this._height/speed;
  this._alpha -= step;
  
  if (this._xscale<500) {
            this._width += 50;
            this._yscale = this._xscale;
   //this.setMask(maskMC);
        } else {
            delete this.onEnterFrame;
   this.unloadMovie();
            this._yscale = this._xscale=500;
        }  
 }
};

However i want to mask the movieclip when it resizes but it doesnt seem to work. I have attached the fla so you can see what i have done. You will need to create 4 images p.jpeg, p1.jpeg, p2.jpgp3.jpg

Thanks

Daniel