[Zope] Manage menu problem

Hi, When i use the Zope management screen i notice that on load in the browser it calls it's own(the server it's installed) IP address when loading the manage_workspace link. This is fine when working with the box directly, but when trying to manage Zope from outside our protected LAN (using a firewall that has a public IP which redirects all request to the Zope box which uses a static private address) the manage screen won't load as it can't find the protected private IP address. Ideally i want to manage my Zope both internally via the LAN and externally from wherever. I was wondering if it's just a config/startup setting as i have noticed some IP settings in the z2.py file. Any pointers would be greatly appreciated. Cheers Nick