Count unique values based on value in another cell in same row

Hi folks,

We have a spreadsheet of people, each have a number unique to them in column B, they can appear in the list more than once. There is a Yes or No on each row in Column AL, sometimes the value in AK is assumed, sometimes an actual value. I need to know the number of individual people for Yes and also for No.

So, I am trying to count the number of unique reference numbers in column B from 5 onwards that also have an answer "Yes" on the same row in column AL, then separately counting the "No" rows. I can use
{=SUM(IF(FREQUENCY(B5:B9999,B5:B9999)>0,1))} or
{=SUM(IF(FREQUENCY(IF(LEN(B5:B9999)>0,MATCH(B5:B9999,B5:B9999,0),""), IF(LEN(B5:B9999)>0,MATCH(B5:B9999,B5:B9999,0),""))>0,1))}
to count how many unique reference numbers in column B. I have looked at a thread from 2009 but couldn't make anything work to count only the Yes or No rows.

Help please, thanks in advance.

Thanks for the replies, and apologies I should have said we use Excel 2003.

Thanks icestationzebra, it gives an answer but I'm not sure the number is correct. It doesn't look right compared to the toal number of unique people.

I have attached a file with a sample of the kind of data.

thanks for your time

unique.xls