Hysteresis basically is a property in which the output is not a direct function of the input. Or there is a lag between output and input. So with a thermostat if you set it to maintain 90 degrees, it may switch on at 87 degree and switch off at 92 degrees. A VE-100 is an on/off thermostat so I don't see how you could hack it to control hysteresis. Generally to control that you would need some form of a Data Aquisition sytem and software to run it. You would then have to "hack" the thermostat somehow (write your own code) to control it and override the current software that is operating it so it never fluctuates away from the set point.