One way to accomplish this would be to loop over the records from top to bottom. Test a variable for the presence of each record's primary key using FilterValues ( ). If the key is present, omit the record and move on. If not, add it to the variable in a return-delimited list using List ( ) and go to the next record.
If you're using version 13, you can make use of the new List Of summary field type to assemble the list of keys quickly. This would give you a quick indicator of duplicates, as you can use ValueCount to find out how many occurrences of the current primary key exist in the found set.
That worked perfectly! Thanks for the help!