Registers a callback function that monitors usage of GUI Library function calls. Once you register such a callback, then when your program calls various functions for example, when it calls ItEv_SetValue), your application's callback function is invoked.

You can use this for debugging an application, for example.

typedef DWORD (CALLBACK *LPFNLOGCALLBACK) (HANDLE hMr,
PPIT_EVENT ppEvt, long fnc_called, long changed,
LPARAM idx, LPARAM word02);
DWORD DLEX It_RegisterCallback (HANDLE hMr,
LPFNLOGCALLBACK lpfncallback);

Returns a pointer to the previous callback function.