i5 DNS server - replacing PC host table entries

Would someone be kind enough to give me some pointers on adding entries to our i5
DNS server?

Our little ten-user network has used the i5 DHCP and DNS servers for years. Last
month we installed a T1 to the new corporate HQ and were given access to a number
of browser-based apps on their internal network. Since we were not given access
to their internal DNS server we've had to use each PC's host table to resolve the
URLs. Currently there are 25 entries for each PC and the list is scheduled to
grow next week. Until such time as we are permitted to use HQ's internal DNS, I'd
like to use our i5 DNS but need a little education. I've read half-a-dozen DNS
tutorials from the internet but can't translate that knowledge to this particular
situation.

Our i5 currently runs a single server "ourdivision" which has a single primary
zone, "ourdivision.com", which defines a few internal addresses and points to our
ISP's DNS for everything else. Since HQ's new URLs have a different domain
"someserver.ourheadquarters.com", they will not fit into the existing primary
zone. Do I just need to define an additional primary zone to the existing server,
or is it necessary to configure an additional server for HQ's new addresses?

Since "ourheadquarters.com" is also a public company with internet access, I do
not want these changes to interfere with existing internet access. That is, if
one of my users launches a URL from her PC (from an emailed link, a favorite, a
web-page or green-screen menu, whatever), I'd like for her PC to first query our
i5 DNS to see whether it resolves to one of the special apps that we've been
given authority to use. If not, then I'd like for her PC to do the normal thing
and go ask our ISP's DNS.

Can someone help me understand what I need to do? Many thanks, JK

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