In order to do this, you'll have to include a second copy of your table in the report. In the Database Expert when you try to add a table that is already in your report, Crystal will notify you that it already exists and let you know it will be "aliased". It will then add the table with a suffix of "_1" in the name.
Assuming that your table is called "Order" and your fields are ItemNo and OrderNo, you would then do the following:
1. Link from {Order.OrderNo} to {Order_1.OrderNo}
2. Set your selection criteria based on {Order.ItemNo}
3. Group on {Order_1.OrderNo}
4. Use the fields from Order_1 in your details section.
-Dell