In the screenshots I show two similar setups with 4 pistons all connected by redstone on blocks directly above the pistons, and a lever over each piston. Turning any lever on will extend all 4 pistons, but which pistons retract when it is turned off again is determined by which lever was used. The screenshots show the results after flipping the left-most lever on and off (-after-1), then the second left-most (-after-2), etc.