Display A Message In Store Procedure

 helo all..., this is my store procedure. but it can not display message. my friend said it must use output code. can someone add output code to my store procedure, so it can display message?
ALTER PROCEDURE [bank].[dbo].[pay]
(
@no_bill INT,
@no_order int,
@totalcost money,
@message varchar(100) -- make it output parameter in your stored procedure
)
AS

BEGIN TRANSACTION

DECLARE @balance AS money



select @balance = balance
from bank.dbo.bill
where no_bill = @no_bill

select @totalcost = totalcost
from games.dbo.totalcost
where no_order = @no_order

if (@balance > @totalcost)
begin
set @balance = @balance - @totalcost

UPDATE bank.dbo.bill
SET
[balance] = @balance
WHERE [no_bill] = @no_bill

-- set @message = 'your have enough balance'
end
else
begin
set @message = 'sorry, your balance not enough'
end

COMMIT TRANSACTION

set nocount off  pls.., thx