[Zope] Putting a default value in an <input type="file"...>

Hi, I got a PageTemplate form with a control scripts. In case of control failure, the form is published again with an error message and the previous values of the fields. This is easy for usual widgets (textfields, radio, checkboxes...) but I'm stuck with <input type="file" value=...> controls, for which I can't give back the previous value (file path in the client file system). Any hint ? I know this is not strictly a Zope problem but I guess some of you already faced that problem. Thanks in advance. --Gilles