Use a union query:
SELECT [Cust_alpha], [Product_Line],[Cust_type], [Analysis_Code], [Total_value],"LastYear" as [FromYear]
FROM lastyear
Union select
[Cust_alpha], [Product_Line], [Cust_type], [analysis_Code], [Total_value],"ThisYear" as [FromYear]
from currentyear
I added the FromYear so...