Count frequency with multiple conditions

[Supermike1983]

I would like to count how many unique values (= the frequency) in column A with the following conditions:

* I only want to include values corresponding to an "X" in Column B
* I only want to count the number of values in Column A which are constantly "Blank" in Column C. Meaning if I have a specific value in Column A with an "X" in Column B occuring multiple times I would like to exclude all these cases if they are not "Blank" in all cases.


In the example below 19, 17, 16 corresponds to these conditions meaning the frequency answer should be =3. But I seem to have a hard time getting rid of the cases where I both have blanks and letters for the unique number in Column A.

Column A	Column B	Column C
19	X
26	X	B
17	X
26 <tbody> </tbody>	X
16	X
26	X
16	X
14 <tbody> </tbody>	X	A
14	X
5	Y	A
7	Y	B
9	Y

<tbody>
</tbody>

 

[Supermike1983]

I know it's a very stupid example but I've switched all the data into something completely else for business-related reasons. Still it's the unique blanks I want to single out and count.