You don't have to get your ISP to organise a static IP for you (AFAIK it's expensive to do that). You can set up a static IP on your computer that your router will recognise. All you need is some info about default gateway, DNS servers etc...have you tried the instructions here?
http://www.portforward.com/networking/staticip.htm

I have a static IP set up for my port forwarding...my normal IP address still changes as it usually would. The static IP is just for port forwarding purposes. If you don't see DNS info, your ISP will be able to give you that. You don't have to say anything about static IPs etc, just ask for your DNS server info. Without a static IP port forwarding won't work for your router.