I have 3 columns: Provinces, Customer numbers, and list of reps
servicing these customers.

A 7213 3
A 8027 8
A 2230 4
B 3240 3
B 3148 3
B 2370 4
C 3121 3
C 3071 3
C 4118 7
C 3125 3

When I filter this list [on provinces], I can tally a total of
different customers I have in a particular province [e.g. for Province
B, the total shows 3].
What I would like to see also is a list of how many reps are active in
that particular province [e.g. for Province B, it would show 2 - reps
#3 and #4; while for Province A, it would show 3 - reps #3, #8, and
#4].

Any suggestion for a formula to achieve this? Thanks in advance!