Dynamic IP services and IP updating

Hi everyone, I've just got my OS X 10.2.3 Server going using Aaron Schurman's NAT Router instructions. I am also using the Dynamic IP service at dyndns.org, and want to be able to notify that service of any changes of my IP on my second NIC. I've tried a couple of the BSD clients, such as ez-ipupdate, however it doesn't support the NICs under OS X. Anyone got any ideas?