Thought it might help to show the SQL for the queries to clarify what I am after.
Version 1
qryPrevReadings
SELECT MeterReadingID, dtMeterReading, MeterID, FuelID, dblMeterReading
FROM tblMeterReadings;
UNION SELECT MeterAdjustmentID, dtMeterAdjustment, MeterID,
FuelID, dblMeterReadingOLD...