This macro defines a message map entry that maps a custom verb to a specific member function of your control.
The resource editor can be used to create custom verb names that are added to your string table.
The function prototype for memberFxn is:
LPMSG lpMsg ,
HWND hWndParent ,
The values of the lpMsg, hWndParent, and lpRect parameters are taken from the corresponding parameters of the IOleObject::DoVerb member function.