[Zope] Dumb DTML question - existance check of an object

Hello, I have a URL, say, /sub1/sub2. How do I check in DTML whether 1. folder sub1 exists or not 2. If not, create it. 3. folder sub2 exists under sub1 4. If not, create it. and so on... Thx http://vsbabu.csoft.net