[Zope] Force DTML evaluation?

[Stefan H. Holek]

I created a Renderable derived ZClass to act as a "content box".
I am basically providing title and content attributes, and when called
like <dtml-var myBox> it nicely renders into an HTML table. 
Then I realised I could not use DTML in the content (type: text). duh!
Is there a function I could use like like 
<dtml-var "do_the_dtml_magic_with(content)">?

My second try was to derive from DTMLDocument but I could for the heck of
it not figure out how to call the baseclass' methods. In python I would
use baseclassname.method() but this seems impossible in ZClasses...

Any insights appreciated,
Stefan