[Zope] help!!! problem with caching zope generated pages

[Robert Rottermann]

Hi there,
I have created a multilingual CMF-site.
To switch the language I use a cookie.
Each multilingual page looks something like this

if lanhuage=GE
  do german ..
else if ..
  do other language
/if

noww my problem:
This works perfectly fine where ever I test but at the site of the guy that
pays the bill.
It is a governemental department that is burried behind firewalls an
proxies.
When one of their user switches the language she have to press the refresh
button to make the change apear.

I allredy have added the following two lines to the header to no avail:
  <META HTTP-EQUIV="Pragma" CONTENT="no-cache">
  <META HTTP-EQUIV="Expires" CONTENT="-1">

what can I do to force a refresh of the screen ????

any help will be much appreciated

Robert