Cross references are not completely Customer Specific.
It depends on the Cross Reference Type selected:
Cross-Reference Type Field
You can select a cross-reference type when you click the AssistButton to the right of the field. The options are:
- Blank: You can enter any cross-reference number and use it to identify the item.
- Customer: The cross-reference number is a number used by a customer.
- Vendor: The cross-reference number is a number used by a vendor.
- Bar Code: The cross-reference number is a bar code that identifies the item
You can also look at the use of Variants for your situation.