Commands Ending Other Commands

[King Nerd III]

I have a commands that runs the rollers outwards and a command that runs the rollers inwards, but if one is running and you call the other one (through pressing a button), then both commands attempt to run at the same time. Is there any way to have each command end the other one when called?
I had an idea where you declare a Command object in the command of the other command (i.e. Inwards has an Outwards Command object in it) and when one is initialized it calls End() from the object, but I don't know if that would work, and don't have the robot electronics board with me to test right now. Any ideas?