[Zope] Struggle to edit dtml in textarea

For some reason if I do the following: <textarea name="col1" rows="30" cols="120" ><dtml-var expr="_.getitem('1_col',0)" html_quote></textarea> I can edit the html but all dtml is interpreted. I am trying to build a dtml page with which I can edit other pages: 1. Any recommendations on how to do this? (example of document_src in dtml?) 2. How do then overwrite the previous page with the edited code? Thanks, Pieter