You can use Webmin to manage domains and subdomains, IF you are using it to do your DNS to the internet. So for instance in GoDaddy you have to give them 2 DNS server (ie. NS1.blah.com and NS2.blah.com) if you are running Webmin on those servers then you can use Webmin. If you are using 3rd party for your DNS .. then it is all controlled at their server.
Oh, BTW SgtM .. have you checked your PMs?