[Zope] HTML - ZOPE?

Hi, I'm not sure if this is a strictly zope question, but I hope some people can give me an idea on how to solve this problem. I'm creating a form which has amonng it's input tags 2 comboboxes. Now, the content of one combobox, depends on the selection of the first combobox. How can I handle this in Zope, Html? Is this even possible in html? I assume, yes if you refresh the page each time the user makes a selection in the first combobox, but how? Thanks, Tom.