Programming "MONEY CONVERTER" ???

Hey everyone,

I'm so new for Java, and I don't know how to make some actions on Java. I'm trying to write a simple Money Converter program, but I don't know where to write calculation codes on this program. I've 3 JTextFields (one for AUD, one for Rate ,and one for USD) and 3 there ActionButtons (USDtoAUD, AUDtoUSD, and Close). I prepared all the stuff (the program screen) except calculations. On this program, I'm gonna enter "AUD" currency rate and then make the calculation to convert it into "USD" value. Let's say float x (AUD value), float y (USD value), float z (Rate). I'm gonna define z as Fixed value, and my input and output will be "x" and "y". [ x(Input)*z=y(Output) ] Where and what should I write to make these calculations in TextField blanks?

Thanks everyone for help.

Pascal