|No offense intended to the other responders... but these answers are a little ridiculous.|
Let me see if I understand...
Small office, 2 PC's
You've already bought 2 usb aircard/evdo devices to get them on the internet and you want them to be able to talk to each other?
Cheapest most effective long term solution?
Return one aircard and buy yourself a router compatible with the model of aircard you have. Linksys, D-Link, Kyocera, Top Global, and Cradlepoint all sell EVDO routers that support various different carriers and models. Many are plug and play.
Plug the aircard directly in to the router.
Connect the two pc's in question via wires or wireless cards to the router.
They share the internet access.
You save yourself roughly $60 a month for the second aircard or you have a 2nd aircard available for home/business trips.
They are now on the same network and they can share a network capable printer or the printer can be shared out through whichever pc it is directly connected to. File sharing can also be set up.
That is the least technical, least expensive, most straight forward way to set up a small network.
@Home PC Repair