How to control "Set Temp" with potentiometer?

Thanks Wana and Terry. Am off to good start with info provided. Will switch from thermistors to water proof DS18B20. An interesting idea to add more temp data. I looked into 20x4 LCD which could present 8 temp points (2 per line)... BUT... am not sure single Ardunio can handle that---seems number of pin ports limits number of temp sensors. OR, is it possible to continuously rotate (loop) sensor selection?---so that theoretically, any number of sensors can be used.