AS2 Drag and Drop - Completion Response

Question

I am making a drag and drop alphabet learning game. There are 27 Movie Clips (letters) in total that are able to be dragged.  I've made it so that 12 of the Movie Clips will drop in a specific DropZone, while the rest will just snap back to their original position.
What I'd like to do is create a completion response that moves to a separate "Good Job!" screen when all 12 Movie Clips have been droped in the DropZone.  How can I do this?  I've searched online for some help but nothing seems to be particularly relevant.
Thanks!

Answer 1

So I've tried adding this code but I still can't get the right result.
My first letter has this code:
food1_mc.onPress=function(){
startDrag(this);
var dropCount = 0;
food1_mc.onRelease=food1_mc.onReleaseOutside=function(){
    stopDrag();
    if (this._droptarget == "/DropZone4") {
            this.onTarget=true;
            _root.DropZone4.gotoAndStop(2);
            dropCount += 1;  // add 1 to the dropCount
            if(dropCount == 12){
                  gotoAndStop("goodjob");  // go to the frame labeled goodjob 
    } else {
            this.onTarget=false;
            _root.DropZone4.gotoAndStop(1)
food1_mc.myHomeX=food1_mc._x;
food1_mc.myHomeY=food1_mc._y;
food1_mc.onMouseDown=function(){
mousePressed=true;
food1_mc.onMouseUp=function(){
mousePressed=false;
food1_mc.onEnterFrame=function(){
if(mousePressed==false&&this.onTarget==false){
this._x-=(this._x-this.myHomeX)/5;
this._y-=(this._y-this.myHomeY)/5;
I've also added what you posted to the other 11 letters.  The first letter seems to work find but all other 11 have lost their ability to snap back into position or drop in the DropZone (they just stick to my mounse after I click on them).  Do I need to change the code for each letter somehow?  I've tried changing if(dropCount == 12){ to if(dropCount == 1){ to test if the one letter that's still dropping can activate the result, and it can't.  I've made sure the frame is named goodjob.  Thoughts?