[Zope] changing properties of a zclass

[Markus Jais]

hello,

maybe this is a too simple question, but I don't know what to do
anymore.

I have a Zclass called "Dokument" and I have an Instance called "Dok" in

a folder.
In the same folder, there is a DTML-Document, from where I call
an external python-method.
The Zclass has the properties "author" and "version".

What I want, is to change the properties of the Instance "Dok" with
the python-method.

I want to do it with the following code:
self = getattr(self, "Dok")
self.manage_changeProperties(Author =  'Bill Gates', Version = '400th
beta')

The method has no error, that is, it does not crash, when it is called.
But the properties are not changed... and I am going mad, slowly but
surely!

Does anybody have a idea, what went wrong????
Thank you very much.

Markus