You can do it. Easily. Whether it'll be accurate is yet to be seen.
http://babel.altavista.com offers a translation service. You could have a script called on each page, before output, which takes the page's contents, checks which language it needs to be translated into and sees if there's a cached version. If not, post the page's contents to babel.altavista.com and get the translation. Save that in your cache file, and display.
That's a simplified version, but if you need more info, please get back to me 😉