TI83plus programming

bfox48

I am a new user of a TI83 calculator and looking for some programming help. I am taking a hydraulics exam next week that is going to require me to solve some fairly complex systems of nonlinear equations. I usually complete these calculations setting up functions in excel and using solver.

Is there a way I can write a function that I can call in the graphing calculator. For example, type...Flow_Area(b,z,y)... then the calclator spits out the answer based on a expression I program based on those variables. Ideally I would like to able able to call these functions from with the solver program that is included in the TI83. If I have to type each full equation in every time I need to solve a system will never finish the test. Any help will be appreciated.

Thanks