How do you get a MS NT DNS server to recieve periodic updates from another DNS server over the internet?

[Matthew]

I have an NT Server running the DNS service and need it to recieve
it's updates from another DNS server over the internet periodically.
Our site presently uses dial on demand ISDN to access the DNS server
and response is very slow due to the dialing up to the ISP before
resolving a host name on the LAN.
How do I get the MS NT DNS server to recieve it's updates from the DNS
server on the net?

thanks in advance

Matthew