title: jquery ui - prevent draggable to be dropped on another  inside a droppable div
body: <p>Im looking for a way to prevent a draggable block to be dragged over another draggable block and vise versa. Or maybe how to detect it's being dragged over it.</p>
  
  <p><a href="http://jsfiddle.net/J7azG/27/" rel="nofollow">http://jsfiddle.net/J7azG/27/</a>
  Thanks in advance.</p>