Called by the framework when the add-in is registered with the Excel Add-in Manager
virtual void OnXllRegister( );
This function is called whenever a user registers the add-in using the Excel Tools - Add-ins dialog. You can use this event to demand, for example, registration information from the user.
Note that since the XLL can be opened directly using the File - Open menu option, this event will not always take place.
The default implementation of this function does nothing.