First of all, you don't need the Google Toolbar to do a site search (although it may have a function that makes it easier, I don't know).
For those who can't make it work, go to Google, click on Advanced search, type your query, then a little lower, under Domain, type "www.officialforum.com". Click Search. It should give you something like this:
http://www.google.ca/search?hl=en&as_qdr=all&q=search+function+disabled+site%3Awww.officialforum.com&meta=
By the way, I tried both Google and Yahoo. Google returns much more results (and relevant ones).
P.S.:
(although it may have a function that makes it easier, I don't know)
Should I have written "has"? 🙂