Wouldn't it be easier to talk to your admins and ask if they can define a rule for you to just your box?
Probably the most restrictive you'll encounter will be just port 80, maybe adding 25 depending on where they stick their mail server. It really might be just as easy to explain what you're trying to do and see if they can offer something.
I was thinking of net connections in various offices & places I might visit, wired & non-wired, wherever I happen to find myself, rather than a fixed location
I'm using 80 & 25, good idea about mail servers though, I'll try POP3, 110.
I use the default port (7647) from anyplace to home, even work, it's the router at home that needs to be configured for a static route to redirect to the Pc that GBPVR is running on.