Cast a spell rotation from one key. Each press of a key can send a different keystroke. You can set a “reset” time so if you stop the sequence, it will reset for next time.
Tap "A" once to get "A", tap again to get "B" and once more to get "C".
If you don't press a key for 1 second (1000ms) the sequence will reset, so the next time you tap "A" you will get "A".