It sounds like you would be well served by managing the incoming data instead of trapping it all and trying to weed it out.
How much easier would this task be if the 2nd, 3rd and 4th card swipes were rejected by the logging system based on appropriate criteria?
Why not trap the swipe into a global field, run a validity check on those values, then create the record and set the 'real' fields only if it passes your check.
Just thinking out loud...
The datasheet is getting data from an Access Database File (.mdb) and the Access Database is a database of the Attendance Machine's Software. So I am not directly connected to it to track live sessions.
And the software has to be manually opened once a day to download the logs from the Attendance Machine through the Software which then stores the data into the Access file.
Please suggest another idea to work it out. I also tried to connect with the Attendance Machine through Filemaker but can't get to know what database is it using in the Machine. the Attendance Machine's Model is 5000A (http://www.biometricchina.com/2-5-fingerprint-access-control.html)
importing the data into a separate table (Temporary usage) then processing each record one at a time with a looing script would accomplish the same thing as connecting FMP to the attendance machine.
This would allow you to query each incoming set of data as to relevance beofre moving the data to the "real" table.
Hate to say it on an FMP forum, but with the system you are currently running, why not simply do it all on your Access Dbase? Then simply migrate the results over to FMP?