[VB.NET] Relazionare piu' tabelle su un DataSet

[illusione]

Ciao
ho collegato due tabelle tramite datarelation
ma quando elimino i record della prima tabella
non mi vengono eliminati i record collegati della
seconda tabella.
Mi puoi aiutare?

        Dim myRelation As New DataRelation _
         ("E", dtSet.Tables("scadenze_settori").Columns("id_s"), dtSet.Tables("scadenze_fornitori").Columns("id_settore"), True)
        dtSet.Relations.Add(myRelation)

        Dim parentColumn As DataColumn
        Dim childColumn As DataColumn
        Dim fkeyConstraint As ForeignKeyConstraint

        parentColumn = dtSet.Tables("scadenze_settori").Columns("id_s")
        childColumn = dtSet.Tables("scadenze_fornitori").Columns("id_settore")
        fkeyConstraint = New ForeignKeyConstraint(parentColumn, childColumn)

        fkeyConstraint.DeleteRule = Rule.Cascade
        fkeyConstraint.UpdateRule = Rule.Cascade
        fkeyConstraint.AcceptRejectRule = AcceptRejectRule.Cascade

        dtSet.EnforceConstraints = True