[Zope] namespace question

Hello. I have a standard_html_header defined in the root folder that looks like this: <dtml-var header.html> So the actual header is keps in header.html which is also in the root. header.html has <dtml-var sidebar> in it. I defined sidebar in the root and override it in sub-folders but it sitll picks up the sidebar defined in the root. This didn't start happened until I did the above trick with standard_html_header and header.html. Any suggestions? I need the header file to have a .html extension so someone can edit them with dreamweaver. Is there an easier way to globally change the name of standard_html_header? Thanks, ^Roman