i found the option to delete duplicates, but i want to delete everything but
duplicates?

i have
column 1 with 2500 names,
column 2 with all the 2500 usernames corresponding to column ones names , and
column 3 with the list of names we need about 600

and i want to filter out of column 1 and 2 all the names that do not match
the column 3 list,
please advice
thanks
ian