Need to multiply a calculated column with existing column

Hi,

I need to multiply the existing column with a calculated column. Please help me know how to do it.

(select DMM_Name, Store_Number, Location,Distbn_Date, Sum(CAST(['+@StoreNumber+'] as Numeric)) TQty,
 PJ_Item_M.SellingPrice,Sum(TQty*SellinpPrice) as Total_T,''CY'' flg  from PJ_Location_M, PJ_Matrix_RowDstbn_T, PJ_Item_M where
 PJ_Item_M.ItemNumber = PJ_Matrix_RowDstbn_T.ItemNumber and
 PJ_Item_M.Variation = PJ_Matrix_RowDstbn_T.Variation

The line

Sum(TQty*SellinpPrice) as Total_T

gives an error: "TQty" Column does not exist