If dtSoll.Columns.Count > 0 Then
                        Dim cols() As DataColumn = {dtSoll.Columns("DATUM"), _
                          dtSoll.Columns("PROFOL"), dtSoll.Columns("TOUR")}
                        dtSoll.PrimaryKey = cols
                    End If

Dim keys() As Object = {r.Item("FERT2"), datum, profol, tour}
                            If dtSoll.PrimaryKey.Length > 0 Then
                                dtSoll.Rows.Find(keys).Delete()
                            End If