Timestamp ONLY when field value changes during import
I'm trying to find a way to log a timestamp when a specific field's value actually changes during a data import. I'm currently using the following setup, which works fine for manual data entry, but always updates whenever the record it belongs to has a matching field during import.
For example. I have a subscriber list that includes the following fields...
The 'EmailAddress' field is the match field for data imports. The data imports always contain all of the existing subscribers plus a small number of new subscribers.
I created two timestamp fields, one each for 'StorePreference' and 'DateLastVisit' with the following auto-enter calculation and "Do not replace existing value…" unchecked.
Evaluate ( "Get ( CurrentHostTimeStamp )" ; [StorePreference] )
As I mentioned, this works great when field data is changed manually, but when data is imported, EVERY record that has a matching 'EmailAddress' field will update the timestamp for both 'StorePreference_Update' and 'DateLastVisit_Update'.
It seems that FileMaker considers any record with a matching field to have all of those record's fields updated, even if the values don't change?
Is there any way around this to get a timestamp to update during data import ONLY when the field's value actually changed?
Thanks for any insight.