[Zope] Validating data entry (dates)

[Henny van der Linde]

Hi,

Is there an elegant way to validate fields in a form before submitting.

For example:

I have a date field. I want to check, before submitting the form, if the
date entered is valid.
Is there someting like a function as: Date.IsValid (I haven a Delphi
background). What I don't want is a Zope generated standard error screen. I
want a custom designed error message/page.

thanks,

Henny van der Linde