ต้องการ ลบค่า2ค่า ใน query ทำไงครับ คือจะหาค่า คงคลังที่เหลือ = คงคลัง-จอง

SELECT     Stocks.PRODUCT, SUM(ISNULL(CASE MarkingDetail.StatusEditRequis WHEN 'False' THEN MarkingDetail.Amount_Requis END, 0)) AS Total, 'รวมจองทุกเลขที่ผลิต ยกเว้นเลขที่5961 จะเขียนยังไง
                      SUM(ISNULL(MarkingDetail.Amount_Requis, 0)) AS Amount_Requis, 'รวมจองของเลขที่5961 
                      SUM(Stocks.Amount + - ISNULL(CASE MarkingDetail.StatusEditRequis WHEN 'False' THEN MarkingDetail.Amount_Requis END, 0)) AS Rest, 'คลัง-จอง ค่าตรงนี้จริงๆจะเอาค่า คลัง-รวมจองทุกเลขที่ผลิต ยกเว้นเลขที่5961
                      Stocks.Amount AS Stocks, Production.ProductionID, Production.CustomerID, Stocks.GradName, Stocks.WeightSize, Stocks.Color AS StocksColor, 
                      Stocks.UNIT AS StocksUNIT, Stocks.Remark, Stocks.MATW, Stocks.MATL, Stocks.MATT, Stocks.Strong, GenerateFG.Fullname, GenerateFG.Model, 
                      GenerateFG.SizeW, GenerateFG.SizeL, GenerateFG.SizeH, GenerateFG.SizeT, GenerateFG.Color, GenerateFG.Charector, GenerateFG.Dwgno, 
                      GenerateFG.Amount AS PDAmount, GenerateFG.Unit, GenerateFG.Charector_Format, Production.DateDelivery, Production.GenerateID, 
                      Marking.Marking_Date, Production.DatePD
FROM         Stocks INNER JOIN
                      MarkingDetail ON Stocks.PRODUCT = MarkingDetail.Product INNER JOIN
                      Marking ON Marking.ProductNo = MarkingDetail.ProductNo INNER JOIN
                      Production ON Marking.ProductNo = Production.ProductionID INNER JOIN
                      GenerateFG ON Marking.GenerateID = GenerateFG.GenerateID
WHERE     (MarkingDetail.StatusEditRequis = 'False') AND (MarkingDetail.ProductNo = '5961')'เลขที่ผลิตที่เลือก
GROUP BY Stocks.PRODUCT, Stocks.CategoryName, Stocks.GradName, Stocks.WeightSize, Stocks.Color, Stocks.UNIT, Stocks.Remark, Stocks.Amount, 
                      Production.ProductionID, Production.CustomerID, Stocks.MATW, Stocks.MATL, Stocks.MATT, Stocks.Strong, GenerateFG.Fullname, GenerateFG.Model, 
                      GenerateFG.SizeW, GenerateFG.SizeL, GenerateFG.SizeH, GenerateFG.SizeT, GenerateFG.Color, GenerateFG.Charector, GenerateFG.Dwgno, 
                      GenerateFG.Amount, GenerateFG.Unit, GenerateFG.Charector_Format, GenerateFG.Charector_Format, Production.DateDelivery, Production.GenerateID, 
                      Marking.Marking_Date, Production.DatePD
ORDER BY Stocks.PRODUCT