Can I assign a new key for fn?

So.

I bought this nifty new bluetooth keyboard.

(a windows based one)

Everything's working great EXCEPT for one thing.

I use a few different apps that have handy shortcuts set as F1-F12.

Normally on my MBP, I'd just have the "Use all F1, F2 keys, Etc. as standard function keys" setting on.

In case you don't know, this therefore forces me to use fn + the function key necessary in order to use the default functions. (i.e. F1 = lower display brightness)

NOW. That being said, I have a couple extra keys on my keyboard, that aren't used by OSX (Print screen, F13-15, etc.)

Is there any way that I could assign these extra keys to be my fn key?

How do I do it?

Would I be able to do this through the system settings? or even the terminal?