notifyinfo (ULONG)
The value of this parameter depends on the value of the notifycode parameter. When the value of the notifycode parameter is BKN_HELP, this parameter is the ID of the notebook page (ulPageId) whose tab contains the selection cursor.
When the value of the notifycode parameter is BKN_PAGESELECTED or BKN_PAGESELECTEDPENDING, this parameter is a pointer to the PAGESELECTNOTIFY structure.
When the value of the notifycode parameter is BKN_PAGEDELETED, this parameter is a pointer to the DELETENOTIFY structure.
Otherwise, this parameter is the notebook control window handle.