[Zope] concatenate in dtml?

I want to put something like this in an index_html method: <dtml-if absolute_url & /Pics> <dtml-var picDisplay> </dtml-if> error message: Invalid attribute name, "&", for tag <dtml-var absolute_url & /Pics> how could it be implemented? then I can have some folders with a Pics subfolder and some without and it is all managed by a single index_html in the root folder. - Bill Kerr