MS Access Math

SELECT [Total] = [Labour Cost] * [Labour Hours] + [VAT]

UPDATE YourTableName SET [Total] = [Labour Hours] * [Labour Cost] + [VAT]

SELECT [Labour Cost],
       [Labour Hours],
       [VAT],
       [Labour Hours] * [Labour Cost] + [VAT] AS [Total]
FROM YourTableName

total: [VAT] + [Labour Hours] * [Labour Cost]