Internet connection sharing

I've got a little bit of a problem setting up my network. I have a desktop upstairs, a desktop in my room, as well as my laptop in my room. My modem and wireless router is upstairs, as that is where the main computer is. I have a wireless connection to my laptop. I have another spare wireless router in my room.
What I need to know is: Is it possible to share the wireless internet connection from my laptop to the desktop in my room?
The only way I can see this happening is by connecting my laptop via ethernet cable to the spare router, and connecting that to the desktop in my room. However, I am not sure if it is possible to utilize both my wireless connection and the physical connection on my laptop simultaneously. Anybody have any advice?