alternating pumps or pump cycles in watercad

Hi everyone.

    I have had addressed this issue before (almost an year ago) but due to some reasons we discontinued working on the project and we started working on it again recently.

I am running an EPS run on a system with three pumps controlled by a tank. Pumps 1 and 2 are smaller ones which pump 700 and 650 gpm and pump 3 is a larger one which can pump up to 1300 gpm. I have my initial tank level at 469. The way i want to run the model is that when the tank level drops to 465, pumps 1 and 2 turn on and fill the tank back up to 469, and when the next time the level drops to 465 pump 3 should turn on and fill the tank up. Is there a way I can make this thing run in this way, so that i can alternate the pumps, like pumps 1&2 for first cycle and pump 3 for next cycle and so on.