Time Machine, Bootcamp, and partitioning my external hardrive

I have a 500GB hard-drive, 200GB of which is full. I also have a 100 GB partition for Bootcamp and I've just bought a 500GB hard-drive for backing up my stuff.

My understanding is Time Machine won't touch the Windows partition. Can I set up Bootcamp so it only uses a partition on the external hard-drive? I was thinking of using 350GB for Timemachine, 100GB for Windows and 50GB for me to play around with.