You can use the following handy technique to perform such a search, among many other search types.
Let's say, you want to find every occurrence of the word "oil" in the
USD/CAD thread under "Forex Trading" forum.
Go to Google (or use the Google toolbar in your browser, if you have it), then click on "Advanced Search":
http://www.google.com/advanced_search
Enter your search term(s) in one or more of the first 4 boxes, as usual. In addition -- here's the trick -- enter, or copy & paste, the thread # in the first box, labeled "with all of the words". In this case, it's 56333. Finally, enter "elitetrader.com" (w/out quotes, of course) in the Domain box. (Next time, with the right browser "forms" settings, as soon as you type "e" or simply double-click in the Domain box, it'll give you a drop-down menu with "elitetrader.com" as a choice.) You'll end up with this search command:
http://www.google.com/search?as_q=o...itesearch=elitetrader.com&as_rights=&safe=off
(Note that some of your Google search defaults could differ from mine; you can always adjust those under Preferences, or click on "Advanced Search" at the top of that screen to edit just the current search.)
Result: all 9 occurrences of the word "oil" in that thread are displayed.
This method works well on ET or any other message board. In fact, it's a lot more powerful than ET's own built-in search, even if you are NOT interested in just one thread. That's because, unlike ET, you can bring to bear the full range of Google Advanced Search parameters, wild cards and logical operators on anything of interest... single or multiple, full or partial words, numbers, phrases, poster's name, dates, file types, thread #s, and so on.