[Zope] 3 level menu + ZPT, suggestions!

[Paolo Dina]

Hi guys.

In my site there is the folder items that contains generic items, 
similar to the following example:

/-items
    +-cars
       +-bmw
       +-maserati
    +-objects
       +-pencil
       +-rubber
    +-colors
       +-red
       +-white
and so on..

i need a navigation menu structured in this way:
a list of main-category links(cars, objects, colors); when i click one 
of them i get various sub-items links, and again, when i click on some 
sub-item i get a description in the main part of the page.

This should explain what i want:
Menù:(when i click objects link)
cars
objects
   pencil
   rubber
colors

Menù:(when i click colors link)
cars
objects
colors
   red
   white

Well, i tried to implement all this "machinery"; when a main-category 
is clicked all works fine.. but when sub-category is clicked menu is 
rendered incorrectly.

I have the example online: http://217.56.213.68:8081/ilmantovano.dev/
and the source too:
http://217.56.213.68:8081/ilmantovano.dev/src/document_src

Thanks for your attention.
Paolo Dina