[Zope] How do you Restrict ZServer socket connections

Hi I've followed anser's How To on "Apache and ZServer (NOt CGI)" and now I have Zope served thru Apache via module ModProxy and the SiteAccess Zope Product. Fine, But Now I want to make Zserver only accept connections from a set of known IP address (ie that where my apache server runs) Any ideas how you do this? I can see there are options to say which ports it listens on but no mention of restricting the IP addresses it allows to connect. Thanks Jon