Ommitting certain records from found count
I'm searching in 2 fields to report a found count. However, I want to restrict the found count using a 3rd field. If there are duplicates in the 3rd field, I only want it to count once, instead of how many times it's duplicated. Is this possible? If so, what is the calculation/script? I'm not even sure if this makes sense. Please let me know.
Thank you much in advance!!!