How to create an interrupt based on potentiometer value(s)?
The typical way that this would be handled to generate an interrupt would be to feed the voltage from the motorized pot into one side of a voltage comparator. The other side of the comparator would be fed from a settable voltage. The settable voltage level would be under software control either from the output of a D/A converter or through use of a digi-pot component. The latter is often the simplest to implement of you find an I2C controlled digi-pot. 

As the motor controlled pot voltage changes it will eventually cross the threshold set by software to the other side of the comparator. This will make the output of the comparator change state. This output is used to generate the interrupt. Since the comparator threshold crossing could be either direction then it is necessary to use an interrupt input that can be configured to generate the interrupt on the positive or negative edge as needed depending on the current circumstances.