Looking for the best way to update a URL that is a IP address that can change.

The site is located on a Cable Modem services. So the IP can change. I like to set up from the ISP ASP pages that point this IP address. To make sure the IP address is right the server running on the Cable Modem will update the IP address when it change.

In the ASP pages, I will have some functions included that redirect to the good URL. I like to know if it passable to have an included file that contains the IP address in the functions library as a included file? This way the server on the Cable Modem as only one file to update, which contain the value of the IP address.

Also how do we specify the path for the included file?