HELP!! onDragDrop getting triggered twice, and I cannot find a way to stop it!

[Nam]

I have set up a onDragDrop event, which when triggered gets triggered twice, once by the item being dropped on, and once by the container for it, which is a dropzone. How can I stop the event from bubbling. I believe that's the term for what's occuring. I tried doing Event.stopPropagation(); but that didn't seem to do anything.