[Zope] product+catalog question

Hi, I have build a external product with its own classes for storing information. How can I get Zcatalog to index the data within these classes and how do I get Zcatalog to index certain parts of these classes (certain dictionaries).

From the ZMI, Zcatalog finds my product but it won't index for instance the tekst field wich is contained in the class. Classes are build on folder or objectmanager.

regards, Henny