Creating a ref coloumn in a sub table

I have 2 tables.

Orders

OrderID
[other columns etc.]

OrderParts
PartID,
OrderID,
Ref,
[other columns etc]

on the order parts column I would like to create a ref field for the orders parts table so the data in the order parts table would look like this.

PartID OrderID Ref
1......43.......1
2......43.......2
3......56.......1
4......56.......2
5......56.......3

Then when I get data from the datatable I can get order by the ref column.

Currently when I insert a new part row I use the following store procedure

DECLARE @Ref int

SELECT @Ref=MAX(Ref) FROM OrderParts WHERE OrderID=@OrderID

IF @Ref IS NULL
@Ref=1

INSERT INTO OrderParts (OrderID, ref [other columns]) VALUES (@OrderID, @Ref, [other columns])

this gets the data in.

But if a row is deleted I need to rebuild the ref column for that order id.

My question; is there a better way to do this? should I be using triggers to handle something like this.

Any help would be greatly apprciated

[edited by: Red_Eye at 12:22 pm (utc) on Oct. 14, 2008]

SQL Server