Another way I have dealt with this is to measure temperature of the LCD with a sensor and a A/D converter input function. Then a display Vee generator is designed around a PWM output from the processor. The software varies the PWM duty cycle to adjust the Vee amplitude. The duty cycle can be derived from the A/D input and translated via use of a look-up-table. This scheme is very nice because it is very easy to make the sensor input control the LCD contrast over a WIDE temperature range when a software translation table can be used.

My experience with a thermistor directly controlling a hardware only Vee generator is that it is very difficult to match the non-linear temperature versus resistance of the thermistor to the non-linear LCD contrast characteristic versus the applied Vee voltage. Particularly if you are trying to match over a range of say -40C to +100C.

Michael Karas