help with IIS

Hi, I'm new with setting up IIS and DNS. I'm having a little problem hosting
a website in the office. I would like to know if what I am trying to do is
possible or if I should do it anothere way. Here is my setup. I will Explain
what I have so far and why I did it so please be patient.

Local AD Domain Name = mydomain.com
Netfirms is hosting the Domain name = mydomain.com --- " internal and
outside domain are named the same.

Running
Server1 = Windows 2003, AD, DNS with IP 192.168.1.2
Server2 = Windows 2003, IIS with IP 192.168.1.4

Server2 IIS Sever has 2 websites
Virtual - IP 192.168.1.4 Port 80 Host Header Value
www - IP 192.168.1.4 Port 80 Host Header Value www.genesispa.com

Server1 DNS Server has the following configuration
Since my Domain name is the same as the hosting I encountered that I was not
able to browse anything that had mydomain.com after a lot of reading I
created the Following DELEGATIONS in order to browse to these addresses.
WEBMAIL,VIRTUAL,SMTP,POP and WWW.

on Netfirms I created 1 A-RECORD so far.
VIRTUAL.mydomain.com and my static IP 99.99.99.99

The virtual.mydomain.com works perfect. internally and from outside the
network.

My question is...
if I create another A-RECORD WWW.mydomain.com with the same static IP
99.99.99.99 on netfrims will IIS know that I'm trying to hit the www website
or will I need to get another static IP. or Do I need an additional record
on DNS
your help is really appreciated.