Called by the framework when Excel opens the XLL. Programmer can return FALSE to halt further loading of the XLL.
virtual BOOL OnXllOpenEx( );
TRUE if the function completes successfully; FALSE otherwise.
This function is called whenever a user loads the add-in, whether using the Excel Tools - Add-ins dialog or directly, using the File - Open menu option.
This is a good time to do any initialization that needs to precede any use of your add-in functions, particularly password dialogs or data loading. Return FALSE to indicate that initialization failed, TRUE otherwise.
If you return FALSE, the add-in will not be loaded and will not be used by Excel thereafter.
The default implementation of this function does nothing, and returns TRUE.