Hjælp! til mit puslespil lavet i adobe flash as3.

Hej jeg er i gang med at lave et puslespil med 6 brikker, problemet er at jeg
ikke kan få musen til at give slip på brikken når jeg fører den
hen til et target.. Jeg ved ik hvordan man mere præcist laver et target så at jeg kan få brikken til at hægte sig fast..
Håber nogen der kan hjælpe.. her er min kode:
var startX:Number;
var startY:Number;
var counter:Number = 0;

piece1_mc.addEventListener(MouseEvent.MOUSE_DOWN, pickUp);
piece1_mc.addEventListener(MouseEvent.MOUSE_UP, dropIt);
piece2_mc.addEventListener(MouseEvent.MOUSE_DOWN, pickUp);
piece2_mc.addEventListener(MouseEvent.MOUSE_UP, dropIt);
piece3_mc.addEventListener(MouseEvent.MOUSE_DOWN, pickUp);
piece3_mc.addEventListener(MouseEvent.MOUSE_UP, dropIt);
piece4_mc.addEventListener(MouseEvent.MOUSE_DOWN, pickUp);
piece4_mc.addEventListener(MouseEvent.MOUSE_UP, dropIt);
piece5_mc.addEventListener(MouseEvent.MOUSE_DOWN, pickUp);
piece5_mc.addEventListener(MouseEvent.MOUSE_UP, dropIt);
piece6_mc.addEventListener(MouseEvent.MOUSE_DOWN, pickUp);
piece6_mc.addEventListener(MouseEvent.MOUSE_UP, dropIt);

function pickUp(event:MouseEvent):void {
    event.target.startDrag(true);
    reply_txt.text = "Drag and drop the puzzle into the box";
    event.target.parent.addChild(event.target);
    startX = event.target.x;
    startY = event.target.y;
}
function dropIt(event:MouseEvent):void {
    event.target.stopDrag();
    var myTargetName:String = "target" + event.target.name;
    var myTarget:DisplayObject = getChildByName(myTargetName);
    if (event.target.dropTarget != null && event.target.dropTarget.parent == myTarget){
        reply_txt.text = "Good Job!";
        event.target.removeEventListener(MouseEvent.MOUSE_DOWN, pickUp);
        event.target.removeEventListener(MouseEvent.MOUSE_UP, dropIt);
        event.target.buttonMode = false;
        event.target.x = myTarget.x;
        event.target.y = myTarget.y;
        counter++;
    } else {
        reply_txt.text = "Try Again!";
        event.target.x = startX;
        event.target.y = startY;
    }
    if(counter == 4){
        reply_txt.text = "Congrats, you're finished!";

   
}
piece1_mc.buttonMode ; true;
piece2_mc.buttonMode ; true;
piece3_mc.buttonMode ; true;
piece4_mc.buttonMode ; true;
piece5_mc.buttonMode ; true;
piece6_mc.buttonMode ; true;
}

Har fundet koden inde på http://www.monkeyflash.com/flash/drag-and-drop-in-as3/