how to drag and drop button to target button in flash

I want to create a button which can be dragged and dropped toward another button so that the button location (x, y) is dragged into the location of the destination button. My code:

sejarah.onPress = function(){
     startDrag(this);}
sejarah.onRelease = function(){
     if(this.hitTest (atarget)){
       this._x = _root.atarget._x;
       this._y = _root.atarget._y;}
     else{stopDrag();}
} 

I want to achieve this: http://www.thibaud.be/#

on(press) {
    startDrag(this);
}

on(release) {
    stopDrag();
    _x = Math.round(_x/_width)*_width + 0;
    _y = Math.round(_y/_height)*_height + 0;
}

This is one of the most simple code that can do a job like this. You put this code inside a button and when you stop dragging this button it's position will snap to the grid.

Your button's clip center must be at top-left corner of button else it can get weird. Also, you can change beginning of grid by changing zeros to position you need.

You can draw a grid to see attachment.