How do I use a WHERE within ORDER BY in SQL

I have an SQL Script where I wouant to ORDER By the Sum of a field where the year is = tp a parameter.

The Table has three (3) years in it, but I want to sort by the sum of the values in only one of the years. The other year will just be data in the record. 

The scripts is: 

SELECT
     "dbo"."Price_Point_Sales_Summary"."ITEM_ID",
     "dbo"."Price_Point_Sales_Summary"."ITEM_DESCRIPTION",
     "dbo"."Price_Point_Sales_Summary"."COMPANY_ID",
     "dbo"."Price_Point_Sales_Summary"."COMPANY_NAME",
    sum( "dbo"."Price_Point_Sales_Summary"."EXTENDED_SALES") as EXTENDED_SALES,
     "dbo"."Price_Point_Sales_Summary"."PRICE_POINT_CODE",
     "dbo"."Price_Point_Sales_Summary"."Price_Point_Desc",
     "dbo"."Price_Point_Sales_Summary"."YEAR"
 
FROM
     "dbo"."Price_Point_Sales_Summary"

Where  "dbo"."Price_Point_Sales_Summary"."YEAR" between 2021 -2 and 2021
and      "dbo"."Price_Point_Sales_Summary"."FISCAL_PERIOD" between 1 and 11


GROUP BY

   "dbo"."Price_Point_Sales_Summary"."ITEM_ID",
     "dbo"."Price_Point_Sales_Summary"."ITEM_DESCRIPTION",
     "dbo"."Price_Point_Sales_Summary"."COMPANY_ID",
     "dbo"."Price_Point_Sales_Summary"."COMPANY_NAME",
   
     "dbo"."Price_Point_Sales_Summary"."PRICE_POINT_CODE",
     "dbo"."Price_Point_Sales_Summary"."Price_Point_Desc",
     "dbo"."Price_Point_Sales_Summary"."YEAR"

ORDER BY
     sum( "dbo"."Price_Point_Sales_Summary"."EXTENDED_SALES") DESC

 The ORDER BY is where I want to be able to sort Descending WHERE  YEAR = 2021 

Can anyone assist

Regards

Gerald