[Zope] How to change site_url

Hi there, Due to a change in my server ipaddress I have to change the site_url of my customized squishdot site. By installatoin squishdot stores the variable site_url somewhere It is not possible to change the site_url in the properties tag of squishdot and I don't know how to change variables in the namespace. Any suggestions will be greatly appreciated. Renier