Returns the name of the active worksheet
static int GetActiveWorksheetName( CString& book_name, bool full_name = false );
A reference to a string that will contain the desired data if the function succeeds.
If true, then the full sheet name will be returned, in the form "[BOOK1.XLS]Sheet1". If false, then only the sheet name will be returned.
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.