i have this Proc 
CREATE Proc  [dbo].Salse_Ditail
    -- Add the parameters for the stored procedure here 
    @Report_Form  varchar(1)  , 
    @DateFrom datetime  , 
    @DateTo  datetime   , 
    @COMPANYID varchar(3), 
    @All varchar(1) , 
    @All1 varchar(1)    ,
    @All2 varchar(1)   ,
    @All3 varchar(1)   , 
    @All4 varchar(1)  ,
    @All5 varchar(1)   ,
    @Sector varchar(10), 
    @Report_Parameter nvarchar(max)
as 
BEGIN 
    -- SET NOCOUNT ON added to prevent extra result sets from 
    -- interfering with SELECT statements. 
    DECLARE @STRWhere nvarchar(max) 
IF @All5=0 AND @All4=0 AND @All3=0 AND @All2=0 AND @All1=0 and @All=1 
    set @STRWhere=  N'and  Sector_id = @Sector'  
if @Report_Form =1 or @Report_Form =3 or @Report_Form =4  
SELECT   RETURNREASONCODEID, SITE,SITE_NAME,Factory_id,Factory_Name,Sector_id,sector_name,Customer_name, 
     Customer_id,ITEMID,ITEMNAME,SALESMANID,SALESMAN_NAME,Net_Qty,Net_Salse,Gross_Sales,Gross_Qty, 
     NETWEIGHT_Gross,NETWEIGHT_salse_Gross,NETWEIGHT_NET,NETWEIGHT_salse_NET,Return_Sales,Free_Good, 
     CollectionAmount   
FROM hal_bas_new_rep  
WHERE   DATAAREAID =@COMPANYID AND INVOICEDATE >= @DateFrom  
    AND INVOICEDATE <= @DateTo and Report_Activti = @Report_Form  
if  @Report_Form =2   
    SELECT   RETURNREASONCODEID ,  RETURNREASONDESC,  SITE , SITE_NAME , Factory_id , 
        Factory_Name ,  Sector_id ,  sector_name ,  Customer_name ,  Customer_id ,  
        ITEMID , ITEMNAME , SALESMANID , SALESMAN_NAME ,    Return_Sales    
    FROM dbo.hal_bas_new_rep  
    WHERE  DATAAREAID =@COMPANYID AND INVOICEDATE >= @DateFrom  
        AND INVOICEDATE <= @DateTo and Report_Activti =   @Report_Form  
        and  RETURNREASONCODEID in 
        ( 
            SELECT     Val  
            FROM dbo.fn_String_To_Table(@Report_Parameter,',',1) 
        )   
        /* 
        @STRWhere   question how i can but the virble here   
        */ 
end 
GO 
i want to but virble put a variable under where Expression and from this function buc I have many function i want to add 
if any one have answer pls send me