First you must have an VAR field to store "something" to compare.

Next you need an calc value to store the "key".

Last you need an filed to store if it's unique or not

The script: ;-)

SHOW all values.
GOTO first record
STORE the the "Key" into "VAR"
LOOP
 goto next record (EXIT after all)
 IF KEY=VAR then set unique to FALSE ELSE set unique to TRUE
ENDLOOP
FIND NOT unique
IF FIND# >= 1 THEN DELETE find records ELSE "DO NOTING"
SHOW all values.

Another way is to create a self join relationship based on a concatenation
of First Name& Last Name & ZIP (call it Duplicate) or some other unique
combination then do a count calculation stored in the field Duplicate_Count
( formula is:  Count(<Filename>::Duplicate) ).

Now create a calculated field called Duplicate_Result and enter the unstored
formula:

 If  (Duplicate_Count>1 then "Duplicate","Original").  This means all
duplicate records will have the word duplicate in this calculated field.
From there it is easy ... just do a find for the word "duplicate and only
the duplicate records will display (do it in LIST or TABLE view mode).

Also, when creating new records, if the field Duplicate_Result is on a
layout as a Merge field then it will display "Original" when the record is
created unless a duplicate(s) exist (once all data in key calculated field
are entered) ... then it will display "Duplicate".  This way, the data entry
operator can see immediately that they have created a duplicate record and
take corrective action before destroying the data integrity in related
records  (i.e., FIND duplicates, verify that records arre in fact the same
and delete the record which was created last).

Later,