[Zope] Problem Getting dtml-with to work

Folder A contains Folder B contains Folder C. If I write in a dtml page in Folder A: <dtml-with FolderB> <dtml-var FolderC> </dtml-with FolderB> then I get an error which states that FolderC does not exist. Why doesn't the above work? I can display Folder C if I click on it in the ZMI or go to it directly via a URL. Folder C is a Plone news smartfolder, if that makes any difference. Is this some behind-the-scenes Plone magic messing me up, or am I misunderstanding what dtml-with is supposed to do?