which internet connection gets used?

I have two nic's on my win 7 pro PC. one connection is to my PC network, which also has Verizon DSL connectivity for the network PC's. the other nic is connected to a Clearwire 4G modem for internet connectivity for this PC.

things are setup this way because I need access to my PC network, but I also need the faster upload speeds that the Clear 4G service gives me.

since both nic's have internet connectivity, how do I know my PC is using the 4G instead of the DSL?

is there a way of limiting the PC to the 4G connection while still being able to see the other network?

is there a way the PC can choose the better of the two connections for what it happens to be doing (using DSL for downloads and 4G for uploads)?