Create Trigger To Check Values At Insert/update

I have never used triggers before and I have tried to solve one problem. If I have the column "currency" in a table and want to make sure that the entered value i valid in relation to another table that contains valid currency formats, I did it like this:

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CREATE TRIGGER [trigger_checkCurrency] ON [dbo].[Client]
FOR INSERT, UPDATE
AS
declare @currency as char(50)
declare @country as char(50)

declare cur cursor for SELECT currency, country
FROMinserted

OPEN cur
fetch cur into @currency, @country
WHILE @@FETCH_STATUS = 0
BEGIN
if not exists(select * from listinfoid where listname = 'currency' and listid = @currency)
begin
set @currency = (cast(@currency as varchar (3)) + ' is not a valid currency')
CLOSE cur
DEALLOCATE cur
RAISERROR (@currency,16,-1) with log
return
end
if not exists(select * from listinfoid where listname = 'country' and listid = @country)
begin
set @country = (cast(@country as varchar (3)) + ' is not a valid contry')
CLOSE cur
DEALLOCATE cur
RAISERROR (@country,16,-1) with log
return
end
else
fetch cur into @currency, @country

END
CLOSE cur
DEALLOCATE cur
update Client set currency = UPPER(currency), country = UPPER(country)
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I use a cursor to handle multiple rows in an update query.
(SQL2000-server)

Is there an easier och better way to do this?
I´m a bit unsure of this code.

Thanx!

/Erik