Sorry, went vba there.
You can add them together easily. Use the query builder to see if you can get your results
TotForDis: [Field1] + [Field2]
and then switch to SQL view to see what it shows
SELECT Table1.Field1, Table1.Field2, [Field1]+[Field2] AS TotForDis
FROM Table1;
This sql adds field1 and field2 and the value is assigned to TotForDis