Add Upsert Row Only If The Record ID Hasn't Been Added Already

My table has a Latest Record checkbox to identify the most recent entry among records with the same email address.  That's the record that I would want updated to trigger a notification when the conditions are met by one ore more of the other records.  I have a pipeline setup with On New Bulk Event as the trigger but the test run lead to the multiple record version of the notification being sent.  Is there a way to only have the Add A Bulk Upsert Row done only if the record id for that row doesn't exist in the "bucket" already?  If so, how do I do that?

I figured I would try to see if I could get the pipeline to work before re-engineering my whole approach to avoid the multiple record version of the notification being sent.  FYI - it's possible and likely that multiple records in the trigger array will have different email addresses, thus, multiple records would need to get the update to trigger separate notifications.  Let me know if I need to provide more details in order to get assistance.

Thanks in advance.