To explain my dilemma, I have a table called Fuel Usage....there are an number of fields, this issue deals with 3 fields..
1) Unit Number
2) Todays End Mileage
3) Last Ending Mileage
I want the Todays Mileage value in the record to replace the Last Ending Mileage next time a record is created for that Unit Number to record Todays Mileage.