May I Connect To A PC On My Network Without It Going To The Internet?

My network includes two desktop PCs connected to the WiFi/WIred router with CAT5 cable, the router then to the DSL modem.  I also have a notebook that connects to the router using Wifi.  I work from my desk (big monitor, etc) but am actually "working" on the notebook, using WINXP Pro Remote feature.  All three PCs obviously have internet access via the router.

Recently got a Verizon PCMCIA internet access card (cell phone access) for the notebook that is running about 700 kbps when mobile.  Is it possible for the notebook to talk to the Wifi router for purposes of being remotely accessed from my desktop but get its internet access via the cell phone data card; and the two PCs to continue getting their internet access through the DSL modem?  I know it doesn't make a lot of sense, other than I am also developing some application software for which it would be very convenient if I could get outside the LAN via the cell card.

Mike