This message is sent to a window that is being dragged over when one of these conditions occur:

• The object is dragged outside the boundaries of the window.
  
• The drag operation is terminated while the object is over the window.

param1
     PDRAGINFO  pDraginfo   /*  Pointer to the DRAGINFO structure for the drag operation. */

param2
     ULONG      ulReserved  /*  Reserved value, should be 0. */