You didn't say what OS you were using. If it is Win XP You can use the Alternate Configuration functionality provided by XP.
You use a mobile computer at your office and at your home. When you are in the office, the computer uses a DHCP-allocated TCP/IP configuration. When you are at home (where you do not have access to a DHCP server), the computer automatically uses the alternative configuration.
To use the Alternate Configuration feature:
On the Start menu, click Control Panel .
Click Network and Internet Connections .
Click Network Connections .
Right-click the local area network (LAN) or high-speed Internet connection that you want to configure and click Properties .
Click Internet Protocol (TCP/IP) and click Properties .
Click the Alternate Configuration tab.
As an alternative, take your sys admin to lunch and convince him/her to assign you a fixed IP at work. Then you can bind more than on IP address to your NIC. You do this from the Advanced Properties of the TCP/IP protocol. If it is a very good lunch you may get the sys admin to help.
Having multiple IPs (w/ appropriate submasks) bound to a single NIC allows the NIC to participate/respond to whichever network it is attached to. If you use different DNS servers at work/home just add all the addresses to the list.
The two rules for success are:
1. Never tell them everything you know.