Safety Button for Firing Cannon

[ruralrobotics]

We have built a four barrel pneumatic t-shirt cannon this year in robotics class that we need to program. We can build buttons for each solenoid to fire but really what we want to do is have a safety button assigned for each barrel. Example: While holding button six down and pulling the trigger on the joystick cannon one goes off. Then release button six and press button five down while pulling the trigger to shoot cannon two. This will prevent any accidental firing of the cannons by accidentally hitting a button. Can anyone screen shot us how to build something like this? Any help would be greatly appreciated.