Hi Peter,
Use a condition as below and statements to perform data
IF MONTH([Order Date])!= MONTH({MAX([Order Date])}) AND YEAR([Order Date])= YEAR({MAX([Order Date])}) THEN "........"
ELSE ......" END
OR
IF DATEDIFF('month',[Order Date], {MAX([Order Date])})>0 THEN "....." ELSE "......." END
Hope it helps!