This message provides the source window with the target window handle and a pointer to the DRAGINFO structure allocated by the source window.

param1
     PDRAGINFO  pDraginfo   /*  Pointer to the DRAGINFO structure allocated by the source window receiving the message. */

param2
     HWND       hwndTarget  /*  Handle of the target window that the drag set was dropped on. */

returns
     ULONG      ulReserved  /*  Reserved value, must be 0. */