Adding font-lock keywords

[Brendan Van Horn]

Greetings!  I spent some time reading FAQs and posts I could find and
I still seem to be missing something.  I'm trying to add some extra
keywords so that they are highlighted while editing.  Here is what I
came up with:

;; windows constants
(setq my-win32-constant-keywords
      (regexp-opt
       '("COINIT_MULTITHREADED" "ICC_COOL_CLASSES" "NULL"
"SW_SHOWDEFAULT"
         "VT_BSTR" "VT_I4")))

(font-lock-add-keywords
 'c++-mode
 '((my-win32-constant-keywords . font-lock-constant-face)))

Where am I going wrong???

Thanks!
Brendan