Hi, I suspect that what I'm about to ask isn't possible to do but thought it was worth a try anyway. Basically, I've got two columns of data within a table. I would like a formula to count only the unique values in one field, but to make things more difficult I only want to count these values if the value in the corresponding field is also a unique value in its field. Is this possible to do without having to add an extra column to perform some calculations first? (this is something I would like to avoid as there are many records and it will slow the spreadsheet down a lot).

Thanks in advance for any help, I hope I've explained myself clearly.