Calibrating the Hall effect sensors for the MTU

I'm trying to calibrate the Hall effect sensors for the MTU but I am having some serious issues. I can't seem to set the mid point of the hall effect sensor in windows. Is the mid point set within windows or is is set within arduino IDE? I am using the sketch that Karl provided on his joystick setup page. I am getting a 0-5 voltage from one direction to the other direction, but I can't seem to set the mid point within windows. When I press calibrate and go through the whole rigamaroll it doesn't seem to want to save that particular point