First regarding error C2660, who have used the MFC version of SetDlgItemText, which is a wrapper for Win32 API. If your function is a member of dialog class then the handle to the dialog is passes as a first param. So to get rid of C2660 pass the handle of the dialog as first param and then pass the next two params. And regarding C2664 the declaration is incorrect. Your callback function should return void with calling convention as CV_CDECL (or equivalent basic calling conevention, check this in your code)
Do your Duty and Don't Worry about the Result