[Zope] Non-ASCII-form-input -> HTML-entities?

I would like to have users being able to enter german vowels ä, ö, ü and other non-ASCII-characters for which HTML-entities exist (ISO 8859-1) into a form-input-field and have them rendered as HTML-entities by the corresponding var-tag in the form-handler. The 'html_quote'-attribute only seems to convert &, <, and > (and quotes?). Of course I could write my own python-method with a lot of replaces. But that would probably mean to reinvent a wheel that already exists (this seems to be a rather common task to me). Or is there a way to do it in DTML? Any help appreciated. Markus Kemmerling