Excel, Find the number of unique values with an extra condition

[greathope123]

A...B
-----
a...0
b...1
c...0
a...1
b...1
there are 5 letters in column A but only 3 values are unique: a, b and c.
Using function, how to find the number of unique values followed by "1" in column B (we know the answer will be 2)?

I will be very appreciated for any helps!

 

[SkipVought]

hi,

1 or "1"?

Two different values.

Does it have to be a formula?

You could use a PivotTable and derive the count from the PT result.

Skip,

_{Just traded in my old subtlety...
for a NUANCE!}