The delay is easy. If you're using an Arduino, just wire up your pot as a voltage divider and do an analogue read of the voltage. Scale that reading up to give you the number of milliseconds you want to delay for, and call delay(). If you really want to choose from one of a set of discrete values (rather than have completely proportional control over the delay) you might want to replace the pot with a switch (link wire, jumper connector ...) to select from the discrete values. Otherwise your timing accuracy will depend on you adjusting the pot perfectly.