Called by the framework to get the name of the DLL containing the add-in functions when they are registered
[C++]
virtual void GetRegDllName(
   CXlOper& xloDllName
);
This value should be populated with the name of the XLL which actually contains the add-in functions.
This method is called whenever the functions contained in a DLL are 
            registered with Excel as add-in functions. You can use it to override the name provided to Excel, when the XLL containing
            the functions has been loaded by a boot-strap XLL. The default implementation of this function returns the name of the XLL
            loaded by Excel (whether using the Excel Tools - Add-ins dialog or directly, 
            using the File - Open menu option).
Header: xllplus.h