Adds or removes an add-in from the working set
static int AddinManager( unsigned short operation_num, LPCTSTR addinname_text, bool copy_logical = false );
Operation_num determines the operation that the add-in manager will perform.
Addinname_text specifies the name or file name of the add-in.
Copy_logical specifies whether the add-in should be copied to the library directory.
Zero if the function has been called successfully; non-zero if the function could not be called. See Error codes for a list of return values.
See the Microsoft Excel on-line Help for full details about this function.