You could try using a temporary table and do something like the ff...
VB Code:
INSERT INTO a ( MasterBL, RefNum, Vessel, Country, Shipper, ArrivalDate, Port, Reg, RegYear, Carrier, ExcRate, CargoLocation, [Container], ShipmentMode, Status )
SELECT DISTINCT ImpMBL.MasterBL, ImpMBL.RefNum, ImpMBL.Vessel, ImpMBL.Country, ImpMBL.Shipper, ImpMBL.ArrivalDate, ImpMBL.Port, ImpMBL.Reg, ImpMBL.RegYear, ImpMBL.Carrier, ImpMBL.ExcRate, ImpMBL.CargoLocation, ImpMBL.Container, ImpMBL.ShipmentMode, ImpMBL.Status
FROM ImpMBL;