easiest way for everyone to do this...(well if your on a Win platform...)

go to www.deerfield.com and download DNS 2 go...it's service that will map a dynamic IP to a static name (???.dns2go.com) Then just make your client use the name to force it to rather than looking up the IP everytime...

That's what I got going and it works on limewire... i'm not sure about other platforms and whether or not they will accept a name instead of a number...