need certificate that works for external name and internal name

Is there a way to get a certificate from MS Cert Server installed on IIS for
Win 2003 so that it works for both external and internal names without
coming up with a warning on one of them about the name?

I have an Exchange 2003 server that I want to use OWA and OMA on, but
securely as possible. I setup SSL fine and I created a certificate using MS
Cert Server to have a valid certificate. This works fine when I go to
https://www.domain.com/exchange and https://www.mydomain.com/oma.

Problem is that I want to make it as secure as possible so I thought I would
setup the mobile phone/PDA users so they have to come in through the VPN
instead of directly from the web. I set it up and This also works fine when
when they try to access the Exchange 2003 server by going to
https://myinternalname/oma. The only issue is the warning. It is not that
big a deal (to me anyway), but I would like to make it so that warning does
not occur.