Peter:
This is a subject you'll have to arrange with your ISP, but as far as I know, is not possible to have a static ip address with a dialup internet access.
At least, here we can't.
You have this two methods
If your ISP could determine or see your modem mac address and modify the settings to asign to this mac always the same IP you're done....! (could be very hard to acomplish)
If you're connected 24 hs a day you already have a static ip address while you stay connected. (depending on your phone rates It could be really expensive)
Solution: get a static connection (asdl; cable, etc) but you still have to ask your isp for a static ip
Hope it helps
Alejandro