The SPFILENOTIFY_STARTSUBQUEUE notification is sent to the callback function when the queue starts to process the operations in the delete, rename, or copy subqueue.
SPFILENOTIFY_STARTSUBQUEUE
    Param1 = (UINT) SubQueue;
    Param2 = (UINT) NumOperations;
 If an error occurs, the callback routine should call SetLastError, specifying the error, and then return 0. The SetupCommitFileQueue function will return FALSE and a subsequent call to GetLastError will return the error code set by the callback routine.
If no error occurs, the callback routine should return a non-zero value.
  Windows NT:  Use version 4.0 and later.
  Windows:  Use Windows 95 and later.
  Windows CE:  Unsupported.
  Header: Declared in setupapi.h.
Overview, Notifications, SetupCommitFileQueue, SetupDefaultQueueCallback