Adding a formula to the selected column will delete all relationships it participates in as a foreign key. (Visual Database Tools)
The column to which you are adding a formula contributes to one or more foreign keys. The modification will delete the attendant foreign-key relationships. Choose Yes to proceed with the modification and delete the relationships. Choose No to cancel the modification.
See Also
Concepts
Error Messages in Visual Database Tools
Other Resources
Computed Columns
Creating Indexes on Computed Columns