DWORD GetDefID();
Call the GetDefID member function to get the ID of the default push button control for a dialog box. This is usually an OK button.
A 32-bit value (DWORD). If the default push button has an ID value, the high-order word contains DC_HASDEFID and the low-order word contains the ID value. If the default push button does not have an ID value, the return value is 0.