>Daniel,
>
>I'm using the function to calculate some totals from other tables and storing the result in a calculated field.
>
>Ideally this should probably be done by using an insert,update trigger, but I'm a bit of a novice here and can't figure out how to pass parameters to the trigger.
>
>In reality it's a bit more complex, but this does illustrate what I'd like to do:
>
>

>Example:
>Table1 Key Reservation_No,CBLineId,AmountTotal
>
>Table2 Key Reservation_No, CBLineId, LineId, Amount
>

>
>On insert and update in Table2 the AmountTotal of the corresponding record in Table1 should be updated with SUM(Amount) where Table1.Reservation_No = Table2.Reservation_No AND Tale1.CBLine = Table2.CBLine
>
>

Using calculated fields instead of triggers is a design question; both will accomplish the same thing, but your either pay the piper on Table2 update (via a trigger), or when you query Table1 (via the calculated field).

To use the former, you don't pass parameters, you query what is in the Inserted table while in your trigger. So, a simple insert trigger for Table2 would be

declare @reservation_no {type}, @cblineid {type}
select @reservation_no = reservation_no, @cblineid = cblineid
   from inserted

declare @amount = {type}
select @amount = sum(amount) from table2
   where @reservation_no = reservation_no, @cblineid = cblineid

update table1
   set amounttotal = @amount 
where @reservation_no = reservation_no, @cblineid = cblineid

Of course, there are some pitfalls here:
1) for performance, you may only want the trigger to fire if any of the three values involved were changed
2) If for some reason the trigger does not properly complete, you will have invalid data

The alternative is to use a calculated field and call a UDF, like you are trying to do. Most likely, you will have to create a specific UDF for each table you want to put a calculated field in.

Hope that helps.
set amounttotal =