Count Unique Frequencies Column A For Pacific Values Column B

I would need to count unique frequencies in column A, but only for a specified value in column B.

Example:

A|B
1|1
1|1
1|1
2|1
2|1
2|2
2|2
3|2
3|2

I am using Excel 2007 and found this formula that counts all unique frequencies in column A: =SUM(IF(FREQUENCY(A2:A10,A2:A10)>0,1))

In my example, result = 3 Now, I would need to add the possibility to count only for B=1; in my example, result should be = 2.