Do you mean, bridge the PC over to the laptop via wifi so it can use the cellular network for Internet access?
If so, you need to do three things.
1. Either configure the laptop's wireless as an adhoc wireless network, or install Connectify
on the laptop (must be runnning Windows 7) and configure the laptop as a wireless AP (access point).
2. Enable ICS
on the laptop's mobile network connection and associate it w/ the wireless network connection so they two will be bridged.
3. Finally, connect the PC to the laptop’s wireless.