[Zope] simple Breadcrumbs modification

[web@3dresearch.com]

Newbie question: I am trying to make a simple modification to this 
Breadcrumbs example:

<!-- start Breadcrumbs -->
<dtml-call "REQUEST.set('rev', [])">
<dtml-in PARENTS skip_unauthorized>
<dtml-let item=sequence-item>
<dtml-call "rev.insert(0, item)">
</dtml-let>
</dtml-in>
<dtml-in rev>
<dtml-with sequence-item>
<a href="<dtml-var absolute_url>">
<dtml-if "hasProperty('nickname')"><dtml-var nickname><dtml-else><dtml-var 
title_or_id></dtml-if></a>
</dtml-with>
<dtml-unless sequence-end>&nbsp;&gt;&nbsp;
</dtml-unless>
</dtml-in>
<!-- end Breadcrumbs -->

I would like to start the Breadcrumbs trail not at the root folder, but 1, 
2 or 3 levels below the root folder.

Thank you for your help.

Janos Dohanics
3D RESEARCH
http://www.3dresearch.com/