[Zope] Is a Global <dtml-with> possible? How can I make <dtml-with> stay in scope forever?

[zvi@12thplanetcafe.com]

Here is my problem: I have a Squishdot instance named
12thPlanetCafe. I wish for visitors to my root Zope
directory's index_html page to go automatically to the
Squishdot instance's index_html page instead. 

Hence I changed the index_html in the root Zope
directory so that it reads:

<dtml-with "_.getitem('12thPlanetCafe')">
<dtml-var index_html>
</dtml-with>

The above change works as long as visitors only visits
the main page at http://12thPlanetCafe.com/index_html.
In that case Zope automatically displays
http://12thPlanetCare.com/12thPlanetCafe/index_html
instead.

However, once these visitors click on any link within
the page the <dtml-with "_.getitem('12thPlanetCafe')"> 
goes out of scope. Instead of being sent to 

http://12thPlanetCafe/12thPlanetCafe/whateverpagewasrequested 

they instead go to 

http://12thPlanetCafe/whateverpagewasrequested.

I really want the <dtml-with
"_.getitem('12thPlanetCafe')"> tag to stay in scope
whenever the user calls a page from a page that itself
was reached using this tag.

Is there any way to do that? I think that this question
relates to the concept of acquisition by context
instead of acquisition by container. I want all of my
pages to acquire the <dtml-with> tag dynamically as a
result of being called from a page in which the
<dtml-with> was active.

If anyone could help me figure out how to keep my
<dtml-with> tag in scope I would appreciate it.