Why dont you just do it as a sub query?

DECLARE @StartYear CHAR(4);

DECLARE @EndYear CHAR(4);

DECLARE @StartMonth SMALLINT;

DECLARE @EndMonth SMALLINT;

DECLARE @TopN SMALLINT;

SET @StartYear = 2014

SET @EndYear = 2014

SET @StartMonth = 1

SET @EndMonth = 3

SET @TopN = 10

select [Customer No.], [Customer Name], [Address1], TEXTSTRE2, [Address2], City, [State], Zip, sum([Sale / Return Amount]) [Sale / Return Amount Total]

from(

SELECT OrdHist.CUSTOMER AS [Customer No.], Cust.NAMECUST AS [Customer Name], Cust.TEXTSTRE1 AS [Address1], Cust.TEXTSTRE2 AS [Address2],

Cust.NAMECITY AS City, Cust.CODESTTE AS [State], Cust.CODEPSTL AS Zip,

CASE

WHEN OrdHist.TRANTYPE=1 THEN OrdHist.FAMTSALES

WHEN OrdHist.TRANTYPE=2 AND OrdHist.FRETSALES = 0 THEN OrdHist.FAMTSALES

ELSE OrdHist.FRETSALES * -1

END AS [Sale / Return Amount]

FROM OESHDT OrdHist INNER JOIN ARCUS Cust ON OrdHist.CUSTOMER = Cust.IDCUST

WHERE OrdHist.YR BETWEEN @StartYear AND @EndYear AND OrdHist.PERIOD BETWEEN @StartMonth AND @EndMonth

--ORDER BY OrdHist.CUSTOMER ASC

) as d

group by [Customer No.], [Customer Name], [Address1], TEXTSTRE2, [Address2], City, [State], Zip

order by [Customer No.]

Thanks,

John