You might want to check out the "continuous" joystick recording function (see guide). This will track the moment to moment position of the joystick on each trial. See also: http://empirisoft.com/support/showthread.php?t=42 re v2006.1.22.

We can't have discreet RTs taken as a function of first motion because there is a certain degree of motion in most joysticks if they are being held--even if the user intends no motion to occur. We set the criterion as it is because it tends to eliminate false alarms without causing missed responses or adding any kind of systematic error to the measurements.