I havent used PC-Anywhere so im not sure if it has to be a numeric ip in order for it to work.
If it supports alphnumeric of web addresses you can use a Dynamic DNS host.
Have a look at http://www.no-ip.com
Basically how it works is you have a domain name that you sign up for (for free)
And you download their software which is a server sitting in your machine which sends your ip address to their website and they assign it to your domain name.
In the end (if all goes well) all you need to type into PC-Anywhere is www.whateveryousignedupfor.no-ip.com
and it will connect to your modem no matter what the ip is