The function guid-equal
compares the GUID data in guid1 and guid2 and returns true if the data is identical.
(guid-equal (com-interface-refguid 'i-unknown)
(com-interface-refguid 'i-dispatch))
=> nil
(guid-equal (com-interface-refguid 'i-unknown)
(make-guid-from-string
"00000000-0000-0000-C000-000000000046"))
=> t
LispWorks COM/Automation User Guide and Reference Manual - 14 Feb 2015