[Zope] default text of dtml-document derived zclass

hi, I just created a zclass which is derived from the dtml-document. The only difference are some additional properties. Now the question: How is it possible to add a default text to an instance of the new zclass? I tried to add a text by dtml after the creation of the instance, but without success. Perhaps someone understands my question and is able to help ... Thanks a lot Marc