[Zope] a warning message before performing an action

Dears, I have a web page with some buttons (<form action=...) to perform some action (by calling a python script). However, some actions (like 'delete' a picture for example) I would like to warn user before performing it. I recall from php how to pop up a window (or a drop down in Mac OSX) with a warning message prompting a 'Yes' or 'No' confirmation and I was wondering how would I do it with Zope, with an example if possible. Any help here would be very welcome. Cheers, Alan