Avoiding duplicate information is database

I've got a small database application that I am working on constructing to put all of the dialup numbers that my company uses nation wide into an easily updated DB. periodically I am sent new lists of numbers and I'd like to be able to eliminate duplicates in the database I'm just not sure how to go about it or better still if anyone knows an application that already serves this purpose or is readily adapted please let me know...as much as I'm enjoying the learning I don't have time to re-invent the wheel Thanks, Jerry Lake - jerryl@europa.com Web Designer Europa Communications - http://www.europa.com Pacifier Online - http://www.pacifier.com