use case condition
ALTER proc [dbo].[K_RT_DateMeatTallyBasedGrid]
@sno int
as
begin
select PN.partyname,Round(DT.totalweight,2) as totalweight,
BT.BirdName,DT.rateperkg,DT.dcno,
CASE WHEN partyname='ClosingStock' THEN 0
ELSE round((DT.totalweight*DT.rateperkg),2)
END AS totalamount
from K_RT_Dailyentryretail DT
inner join K_RT_PartyName PN on PN.sno=DT.partyname
inner join K_RT_BirdType BT on BT.sno=DT.BirdType
inner join K_RT_WarehouseDetails WD on DT.branchdate=WD.sno
where DT.branchdate=@sno order by WD.[date] desc
end
may be it will help u