Assuming [GI1] is in a table called 'tblData'.
UPDATE tblData SET tblData.GI1 = "A " & Right([GI1],Len([GI1])-2)
WHERE ((CDate(Right([GI1],Len([GI1])-2))<Date()) AND (Left([GI1],2))="B ");This will update any row that starts with "B ", anot not "B". Just in case you had any other text starting...