fluctuate between (someone and someone else)
to waver between choosing one person and another. I am fluctuating between Sam and Tony as my choice. The manager fluctuated between Mary and Sarah as the new assistant.
fluctuate between (something and something else)
to move between one thing and another; to change from one thing to another. Things seemed to fluctuate between the very good and the very bad. The temperature in here fluctuates between too hot and too cold.
fluctuate with something
to vary in accord with something. The tides fluctuate with the phase of the moon. Frank's blood pressure fluctuates with his mood.