navigating a web interface with a shell script

I'm trying to design a script that will check the external ip address of my home network and then assign it to the A record of a subdomain. When i started, i thought i could do this with SSH, but turns out I don't have ssh access to update the DNS record (not surprising i suppose)

So now, i have to figure out if it's possible to log in and navigate the web interface with a script( perl or bash preferably) to update that A record. I don't even know where to start on this, and was hoping maybe someone here might be able to point me in the right direction. I've so far managed to find nothing online, but I think it's at least partially because search with script and web interface tend to bring up cgi type threads.

Thanks again!

No-IP - Dynamic DNS, Static DNS for Your Dynamic IP provides software to do this so no need to do the work.

the plan is to be able to run the script from a mobile device. also, it seemed like a interesting project (my motivation for most things i do)