unique records from 2 long spreadsheets

(I posted this question in the Excel functions forum, but I'm not really sure that's the right place) I am an Excel novice, so I hope this is the right place for me. I have a list of about 50,000+ rows of names (that I can reduce to 20,000+ if I have to). The list has about 15 columns with various information - address, phone, county, license number, several dates, etc. I get this list sent to me once a month. What I need is to find just the new names on each new list. The license number is the only thing I have found that both stays the same and is unique to each person, so I can use that as a filter, but if I use an advanced filter/unique records only, I will get names from the old list that are not on the new list which I do not want. Is there some way I can do this without taking all day and making my eyes cross?

Laurie

Thanks, but I am novice enough that I didn't understand those formulas. Also, what I want is only the new names, not the duplicate ones. Example:

list A
Sue Adams
Bob Bennett
Joe Smith

list B
Sue Adams
Jack Jones
Joe Smith

list C
Jack Jones