I am wanting to get into some deeper TI-85 prgramming. Yeah, I know, this is a REALLY old calculator, but it works better than the crappy TI-83s that the school provides. Anyway, I need some help writing a program that would solve more complex Algebraic and Calculus-related problems. things like Functions would be especially nice. If anyone has any knowlege relating to this topic, or if you know of any good FAQs, please fill me in. Google doesn’t return a whole lot of results about this particular model… thanks 
If by functions, you mean subroutines, it looks like you can call other programs as if they were subroutines:
http://education.ti.com/product/pdf/gb/8516eng.pdf. Page 19, I think.
More info at http://education.ti.com/product/tech/85/guide/85guideus.html