Yes, it should be possible. You need to set up the Mobile Broadband dongle in the PC then enable "Internet Connection Sharing" on the connection.
Create an "Ad Hoc" wireless network between PC and Laptop and the Laptop will have internet access provided the PC is running and online.
I have a couple of tutorials on this:
Setting up an “Ad Hoc” wireless network with Windows XP click here
Setting up an “Ad Hoc” wireless network with Windows Vista click here