Identity And SqlDataSource Question

I'm trying to update my e-commerce approach from ADO-heavy code to a more modern approach based on the SqlData Source.  I also want to move away from Stored Procedures for the moment, if I can, though I may return to them later (mainly for educational purposes at the moment). 

In the past I used @@Identity in a stored procedure to return an ID# which I passed on to the end user as their "order number".  Unfortunately this approach seems to only apply to SPs.

In short, what's the best way to handle this using SqlDataSource and minimal ADO code? 

Just to add a bit more detail, I've got basically three tables, in a fairly obvious relationship.  Orders stores the main order info (Customer's name and address, total, etc), OrderDetails lists the line items, and Products contains detail on the items.

(Put another way, the auto-generated tags in the SqlDataSource object either don't include the OrderID param because it's toggled for Identity in the database, or if I toggle Identity off then I don't know how to trigger it to toggle the next number in sequence.  And either way I don't know how to feed that information back to the program.)

Thanks!