Finding duplicates

In my workbook, I have two columns. One column is customers that have purchased machines in our counties...the other column is customers in our database that live in those counties...how do I set up a column that shows the duplicate customers so we know who is in our counties that have not purchased a machine?

try writing a macro with vlookup function...

Will this formula work for you.

Column A would be the column of customers who have purchased machines.
Column B would be the column of customers that live in the counties.
Column C is where you paste this formula, display the results, and you can change the quotes to what ever messwage you want.

Cell C1

=IF(COUNTIF(A1:A999,B1)>0,"Have Purchased","Have not purchased")

Cell C2

=IF(COUNTIF(A1:A999,B2)>0,"Have Purchased","Have not purchased")

etc