Build me an Android apllication (Calculator)

I want an android application i.e., Calculator. It will not be an ordinary calculator. It will calculate a specific parameter while entered certain inputs. The Parameter and the inputs will be linked with each other through a very simple equation. We just have to input certain data in the calculator and the equation will calculate behind black box and directly show the result to the user without letting the user calculate manually. After the work is done, I will very much appreciate if i can have the codes as well.