From your description, this is the structure I would start out with. I drew this out on paper first, then created the tables.
One
order can have many
deliveries, and one
delivery can have multiple
order details (items).
The field names ending in "PK" are for linking tables and shouldn't be displayed on forms/reports.
The two fields "WorkOrder" and "DeliveryNum" are for you to assign your numbers (roll your own number scheme - automatic or manual).
Attachment 9505
The main form's record source would be a query based on the table "Orders".
A sub form's record source would be based on a query based on the table "Deliveries"
A sub sub form's record source would be based on a query on the table "Order_Details"
I could do that..... but then you wouldn't have the fun or get the experience..
