Is it possible to increment an Column in MS SQL inside a WITH and CASE WHEN statement.

Is it possible to increment an Column : Stock_product in MS SQL inside a WITH and CASE WHEN statement.

I am attempting to sum amount products per day (Column : sum_Per_Day) in my table to get Column : Stock_product (Desired results) but I get Stock_product and the result  that running from old order number and it wasn’t what I had hoped for.

My code:

WITH SourceD_ AS (
SELECT b.Orders
,b.shop_no
,b.d_Date
,b.product_no
,a.product_name
,b.Chk_Order
,b.sum_Per_Day
,lag(b.Chk_Order) OVER (ORDER by b.Chk_Order , b.Chk_date) AS Prev_Chk_Order
,lag(b.sum_Per_Day) OVER (ORDER by b.Chk_Order , b.Chk_date) AS Prev_sum_Per_Day
,ROW_NUMBER() OVER (ORDER BY b.Chk_Order , b.Chk_date) AS rn
FROM db_datatest b LEFT JOIN db_Mastertest a ON (b.product_no = a.product_no)
WHERE b.d_Date > getdate()-374)
),
SumD_ AS (
SELECT 
*,
SUM(CASE
WHEN (Chk_Order != Prev_Chk_Order) THEN sum_Per_Day
WHEN (ISNULL(sum_Per_Day,0) != 0) THEN sum_Per_Day
WHEN (ISNULL(sum_Per_Day,0) = 0) THEN 0
ELSE 0
END) OVER (ORDER BY rn ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) as Stock_product
FROM SourceD_
)
SELECT 
*
FROM SumD_
ORDER BY rn;

I want the following result Column : Stock_product (Desired results)
by If the orders number changes (new orders number) should use value from column : Stock_product calculate on base column : sum_Per_Day to create new value of column : Stock_product

 

Best regard.