Bootcamp space is full, Can I use an ext HD...PLEASE HELP!!!

Ok so, for the purpose of my college classes, I've partitioned my MacBook HD with bootcamp and installed Windows 8.1. I then installed Microsoft Office 2013 because I specifically needed it for the class I'm enrolled in. My issue is, when I set up the initial partition, bootcamp would not allow me to allocate more than 20GB for the Windows side. This obviously became a HUGE problem once everything was installed and I began work on my papers; I'm constantly getting the "Low Storage Space" pop-up. Long story short, I'm down to a pathetic 10Mb free in Windows. I cant import and download the necessary files for completing assignments because there is absolutely no free space.

I saw an idea online somewhere where someone used their extHD and set it up with 3 separate partitions. They made one for Time Machine, one for general storage and one for Windows. This made me wonder if I can do the same thing and somehow divert everything (going forward) to my extHD. All my temp files, downloads, basically EVERYTHING accept for the necessary program files for Windows 8.1 itself and Office (which obviously need to stay native to the machine). Does this make sense? I dont know why bootcamp would not permit me to give the windows side more space but I thought I would try this before I wiped everything and went all the way back to that point. ANY help would be incredibly appreciated as Ive spent some very long hours trying to figure out a solution.