How do I invert an input axis using Javascript?

I would like to create a boolean option for selecting whether the axis for MouseX and MouseY is inverted or not. I can obviously change this from within the Input Manager, but I would like to do this using the Unity GUI. I couldn't find anything in the scripting references.

Any help would be greatly appreciated.

Have a boolean variable which determines whether the input should be flipped. You can then simply multiply the Input value by -1 if the boolean value is true. Something like this:

var flipY = false;

function Update() {
    var inputY = Input.GetAxis("Vertical") * (flipY ? -1 : 1);

You can then change "flipY" to true, and the inputY values will be reversed.