[Zope] ZClasses and aquisition

Hi there, I created a Zclass that renders some data and displayes it. I use DTMLMethod as one of its base classes. One of the classes methods is called index_html. This method calls the rendering function. So http://..../myInstane works fine. However when I want to embed the output within an other page I either get the wrong output, or an error. using: <dtml-var myclass> produces just the content of the DTMLMetho (instead of rendering it first). <dtml-var expr="myclass.index_html()"> claimes that the rendering function I defined in the class are not defined. So how can I use my ZClass like a function, or how can I embed its output in an other page?? thanks Robert