I have three rows of data in Say Col A, Col B and Col C

Col A has values W,X,Y,Z
Col B has values 1,2,3,4 ... 50.
Col C has names of customers.

There are about 300 records, thus multple numerical values in 4 categories
of W, X, Y and Z. There are also repeating values of numbers for a given
category.

e.g. Category W has 1,3,28,1,1,34,1,45,2,5,2,2,6 etc in Col B and Col C has
diff customer names.

Thus although here category W has 13 records there are only 8 unique values
in Col B.

If I filter on Col A for category W, I get 13 rows. How should I filter, use
formula or sort or something else, that will give me unique values of Col B
when I filter on Col A.

Thanks in advance.