Drag & Drop Event capture

Hello,
I'm looking for a way to intercept, capture in firefox a Drag and Drop event in the CKEditor (3.x), like I can do it with a paste.
I've seen some javascript code like the one below, which works perfectly outside the editor, but not when I drop some text inside the editor.

<script type="text/javascript">
  function dragDropListener( evt )
  {
   alert( "Drop Event Captured!" ) ;
   evt.preventDefault() ;
   evt.stopPropagation() ;
  }

function init()
  {
   window.captureEvents( Event.DRAGDROP ) ;
   window.addEventListener( "dragdrop", dragDropListener, true ) ;
}
</script>

Thanks in advance