A low-tech approach is to use the recently added feature called Actions.
You will find that menu option under settings for the table.
You could have a checkbox that says copy to other table. Then you can have an action trigger when the record is saved and that field has changed and it is set to checked.
Then configure the actions so that each individual field is mapped to the correct field in your other table.
I would suggest that you put a report link field on your main record which will show an embedded report of all of the employees with the same employee number in your archive table. That way you can refresh the main record and see that the archived record was successfully created. Then you can delete the original record manually with confidence, knowing that the archive record was successfully created.
Note that if you do you add fields to your main record, you will also have to remember to create those equivalent fields on the archive record and adjust your Action.
