Need a little help with this script!

programming flash
1

Hey there, i need a little help with this transition script below!
It’s a neat mask transition on mouse click!
The Script works perfect as i want it to, BUT i need to resize the area where the user can click with the mouse to make the transition happen! Because the images are only the size of 200266 but the whole stage has the size of 900600! Now when i click anywhere on my stage the transition starts, but i only want it to start when the user clicks exactly on the image! Maybe someone of you pros can find where this is defined below!

thx in advance

Stage.scaleMode = 'noScale';
var speed = .2;
var delay = 2;
var switchblur = 9;
var images = ["hil", "ice", "mtn"];
var index = 0;
var transbmp = new flash.display.BitmapData(266,200);
var blurfilter = new flash.filters.BlurFilter();
loadTransBitmap(images[index]);
var clips = createGrid(this, 1, transbmp, 30);
function onMouseDown(){
 index++;
 index %= images.length;
 loadTransBitmap(images[index]);
 startTransition(clips, transbmp, speed, delay);
}
function loadTransBitmap(id){
 var tempbmp = flash.display.BitmapData.loadBitmap(id);
 transbmp.copyPixels(tempbmp, tempbmp.rectangle, new flash.geom.Point(0,0));
 tempbmp.dispose();
}
function createGrid(target, targdepth, sourcebmp, size){
 var home = target.createEmptyMovieClip("transition_mc", targdepth);
 var depth = 0;
 var clips = new Array();
 var row, rows = Math.ceil(sourcebmp.height/size);
 var col = Math.ceil(sourcebmp.width/size);
 var mc;
 var offset = new flash.geom.Point(0,0);
 while(col--){
  row = rows;
  clips[col] = new Array();
  while(row--){
   mc = home.createEmptyMovieClip("grid"+row+"_"+col, depth);
   mc.rect = new flash.geom.Rectangle(size*col, size*row, size, size);
   mc._x = mc.rect.left;
   mc._y = mc.rect.top;
   mc.rotate = 0;
   mc.speed = 0;
   mc.bitmap = new flash.display.BitmapData(mc.rect.width, mc.rect.height, true, 0);
   mc.bitmap.copyPixels(sourcebmp, mc.rect, offset);
   mc.attachBitmap(mc.bitmap, 1);
   mc.transition = null;
   clips[col][row] = mc;
   depth++;
  }
 }
 return clips;
}
function startTransition(clips, sourcebmp, speed, delay){
 var row, rows = clips[0].length;
 var col = clips.length;
 while(col--){
  row = rows;
  while(row--){
   clips[col][row].onEnterFrame = transOnEnterFrame;
   clips[col][row].transition = sourcebmp;
   clips[col][row].rotate = -(delay*(col+row)/2)/Math.PI;
   clips[col][row].speed = speed;
  }
 }
}
function transOnEnterFrame(){
 this.rotate += this.speed;
 
 if (this.rotate < 0) return;
 if (this.rotate > Math.PI){
  this.rotate = Math.PI;
  delete this.onEnterFrame;
 }
 
 if (this.transition && this.rotate >= (Math.PI/2)){
  this.bitmap.copyPixels(this.transition, this.rect, new flash.geom.Point(0,0));
  this.transition = null;
 }
 
 var sin = Math.sin(this.rotate);
 
 var matrix = new flash.geom.Matrix();
 matrix.tx = this.rect.left + sin*this.rect.width/2;
 matrix.ty = this.rect.top + sin*this.rect.height/2;
 matrix.b = matrix.c = -sin/2;
 matrix.a = matrix.d = 1 + matrix.b;
 this.transform.matrix = matrix;
 
 blurfilter.blurX = blurfilter.blurY = Math.floor(switchblur*sin);
 this.filters = [blurfilter];
}