[Zope] getitem?

Hello, I tried <dtml-let item="sonstiges.help.sonstiges.err.getitem(_.str(httpcode))"> <dtml-if item> <dtml-var "item.title()"> <dtml-else> NO ITEM </dtml-if> <dtml-let> My "err" folder as several of DTML Methods which give an explanation for every HTTP error code. I want to retrieve that explanation. It has to be failsafe in cases where an explanation for the errorcode is missing. What is wrong with my code? Any ideas how to solve the problem? Thanks Ulrich