I'm trying to write a formula to produce results such as:

AA 1
BB 0
BB 0
AA 2
AA 3
BB 0
AA 4
CC 0

Column A is a (drop-down) data validated list of 'AA,BB,CC'.
Column B is the counter cell.

Every 'AA' increments a counter, anything not 'AA' yields a 0.

I've tried using the countif but it seems to give me a sum rather than what I'm looking for, at least to what I understand its use of from the help.

Is this possible in a formula? I'd rather not have to use VBA code if at all possible.