I set this file up like suggested but everytime I import it still imports all the data thus duplicating my data in FM. What am I doing wrong?
This was the suggestion:
In order to import only data that has changed or is new, you need to have a way for Filemaker to match incoming records against existing records. This is usually accomplished by have a unique record identifier or serial number, so for instance you could have a column in the spreadsheet that has an auto-incremented serial number that is always unique and never duplicated. The FileMaker table also needs to have a field for this serial number or identifier.
When you import the data, instead of doing a normal "Add Records" import, you use a matching import, setting the Serial Number in FM to = the serial number in the spreadsheet. You would then check "Update matching records in found set" and also check "add remaining data as new records". That means that any records in FM that have matching serial numbers will be updated and any incoming records (rows) in the spreadsheet that do not have a matching serial number in Excel will be added to FM and be available for matching in the future.