Column <Columnname> is a computed column, and cannot participate in indexes or relationships. (Visual Database Tools)
You tried to use a column with a formula in an index or relationship. In SQL Server 7.0 databases, a computed column cannot participate in an index or a relationship. In SQL Server 2000 and higher, a computed column can participate in indexes, but not in relationships. Either clear the column's Formula property or remove the column from the index or relationship.