Webmin and Usermin responding to one domain name

I was looking around Webmin configuration. As much as I figure, I can setup from which IP address must requests come so Webmin would respond. We need this situation. We have several sites up and running with different domain names, configured over Virtualmin, but we want that users can login from only one of those websites (let's say only if i go to https://www.site1.com:10000, even though i am also running www.site2.com on the macihne). From there we want to administer all sites. And of course, if we logged in from 1 certain IP so we can administer it locally. Same thing would be great to setup for FTP and Telnet access ... Is it possible? Thanks :)