Preventing multiple submits

Hi,
on my website, there is a form where users can submit data to the
site. I was just wondering if there was a simple (server-side) way to
check if the user has already submitted something and preventing him
from submitting the same thing twice (because he clicked on 'Submit'
multiple times because the site took a little longer to load, or
something along those lines). Can you achieve this in mod_ruby without
resorting to more than moderately complex measures?

-- 
Bye: Andi S.                          mailto:[email protected]