NaN message help!

Hi everyone,
I’m fairly new to Flash and I apologise in advance if what about to ask is either silly or obvious (or both!)…

I want to create a simple Flash calculator but I am having problems with VERY basic numeric expressions.

At the moment (please see attached .zip file containing .swf and .fla) I just have two text boxes and a button. One text box takes a number from the user and when they press the button, it outputs that number multiplied by 2 in the second text box.

BUT no matter what I do, I ALWAYS get “NaN” as the output for the second text box. My ActionScript for the .swf is as follows:

enter_btn.onRelease = function() {
    outputNum = inputNum * 2;

var inputNum:Number = 0;
var outputNum:Number = 0;

Any help would be very welcome!

Many thanks,