hwnd (HWND)

Window handle of a sender.

DdeStruct (PDDESTRUCT)

DDE structure.

This points to a dynamic data exchange structure (see DDESTRUCT). offszItemName identifies which data update request is to be retracted. If this is a zero-length string, data update requests for all items are retracted.

ulReserved (ULONG)

Reserved value, should be 0.