find unique values in a range that contains text and empty cells

Hi,

I am trying to count the number of unique values in column B, given a certain criteria in column C. Both ranges are text. Column B may have empty values.

I have tried the following formula but cannot find a way to add an IF for the criteria (column C):

=SUM(IF(FREQUENCY(IF(LEN(B2:B100)>0,MATCH(B2:B100,B2:B100,0),""),IF(LEN(B2:B100)>0,MATCH(B2:B100,B2:B100,0),""))>0,1))

Have also tried the below formula, but doesn't work with empty cells in Column B:

=SUM(IF(FREQUENCY(IF(C1:C100="A",MATCH(B1:B100,B1:B100,0)),ROW(B1:B100)-ROW(B1)+1),1)).

Help please?

Thanks!!

Nic