[Zope] metal strangeness

Ok, can someone suggest a better way of saying this: <span omit-tag="" tal:define="skin here/getSkin ; locSkin here/getLocationSkin ; nonavbar python:1"> <metal:block use-macro="here/skins/${locSkin}/pagelayout/macros/${skin}"> According to my reading of the docs, either use-macro="here/skins/?locSkin/pagelayout/macros/?skin", or the above, should work. Certainly, here/pagelayout/macros/?skin works, but if I put a ?locSkin in the middle of the url, it complains about a list() operation over a non-sequence. By my reading of the specs, metal attributes should use the tales syntax, and the tales syntax says the above (first) is valid, I think? Any suggestions/help greatfully accepted ;) KJL