[Zope] Iterating over REQUEST.form

Hi all, I'm sure somebody more clever than me can work this out. I'm getting results back from a form (checkboxes), so I never know how many items I am going to get back. What I want to be able to do is iterate over the contents of REQUEST.form to be able to process each item, no matter how many results I get from a form. Is there a way of doing this (I'm definitely sure there is but I'm not seeing it), or perhaps there is a better way. Thanks in advance, David