[Zope] Sequence number inside a tree

Hi, Is there a way to generate a sequence number inside a <dtml-tree> or replace the + sign with a sequence number? What I wanted to do is something like this: 1. Branch_1 1.1 Branch_1.1 1.2 Branch_1.2 1.2.1 Branch_1.2.1 2. Branch_2 2.1 Branch_2.1 2.2 Branch_2.2 Tks. AL