ControlPanelDefProcPtr

ControlPanelDefProcPtr
Header:	Processes.h		Carbon status:	Unsupported

typedef SInt32(* ControlPanelDefProcPtr) (
    SInt16 message, 
    SInt16 item, 
    SInt16 numItems, 
    SInt16 cPanelID, 
    EventRecord *theEvent, 
    SInt32 cdevValue, 
    DialogPtr cpDialog
);

You would declare your function like this if you were to name it MyControlPanelDefCallback:

SInt32 MyControlPanelDefCallback (
    SInt16 message, 
    SInt16 item, 
    SInt16 numItems, 
    SInt16 cPanelID, 
    EventRecord *theEvent, 
    SInt32 cdevValue, 
    DialogPtr cpDialog
);