so here is what to do, i know what to do but not the exact button clicks to do it.
1. Set up the network settings on your computer so that it always has the same ip address on your network
2. In your router settings port forward 9091 (i think that's the transmission port) to the ip you used for your computer
3. Now if your isp gives you a dynamic ip adress go to dyndns and set up a free account
4. When you want to access the web interface just type int your_external_ip_address:9091 or your_dyndns_url:9091
just so you know, I have been using the web interface recently and it isn't very stable, maybe it will be more stable on intel computers but on my g5 it crashes a lot with the web interface enabled.