Drag and Drop - Help please

I have created a drag and drop class that is attached to a movie clip as its base class.

I would like to have a button that enables me to toggle the drag and drop property for the movie clip on and off, for example one user might want the movie clip in one position on screen whereas another person would want a different position for the clip. The button will allow the user to switch drag and drop off and on as they please, rather like a locking and unlocking feature. I have attached the code for the class and the code i have scripted for the buttons, any help anyone could offer would be appreciated?

The code i have compiles with no errors but the drag and drop does not stop, does anyone know of a way to kill and then reinialize the drag and drop class with mouse events?

Regards

Liam.

package
{
import flash.display.MovieClip;
import flash.events.MouseEvent;
import flash.text.TextField;
public class DragDrop extends MovieClip
{
public function DragDrop()
{
this.addEventListener(MouseEvent.MOUSE_DOWN, dragMovie)
this.addEventListener(MouseEvent.MOUSE_UP, dropMovie)
}
private function dragMovie(event:MouseEvent):void
{
this.startDrag();

}
private function dropMovie(event:MouseEvent):void
{
this.stopDrag();
}
}
}

//Button Code

keyboardDragMC.lockBtn.addEventListener(MouseEvent.MOUSE_DOWN, Lock);

function Lock(event:MouseEvent):void
{
keyboardDragMC.stopDrag();
}

keyboardDragMC.unlockBtn.addEventListener(MouseEvent.MOUSE_DOWN, Unlock);

function Unlock(event:MouseEvent):void
{
keyboardDragMC.startDrag();
}