my code
-------
  ada.Fill(ds, "reports.renewal_contact_t ")

                ds.Tables(0).DefaultView.RowFilter = " PHONE NOT like'0'"
                dt = ds.Tables(0)
                For Each q In dt.Rows
                    chkphone = q("PHONE").ToString
                    chkdphone = Regex.Replace(chkphone, "[^d]", "")

                    'MessageBox.Show(chkdphone)


                    If (chkdphone.Length = 10) Then
                        Dim anyRow As DataRow = dt2.NewRow
                        anyRow(0) = chkphone.ToString
                        dt2.Rows.Add(anyRow)

                    ElseIf (chkdphone.Length >= 10) Then
                        rsltstring = chkdphone.Substring(chkdphone.Length, -10)

                        Dim anyrow1 As DataRow = dt2.NewRow
                        anyrow1(0) = rsltstring.ToString
                        dt2.Rows.Add(anyrow1)
                    Else


                    End If
                Next

                new_ds.Tables.Add(dt2)
                ComboBox1.DataSource = new_ds.Tables(0)
                ComboBox1.DisplayMember = "PHONE"



 Error
 -----
 length cant be less than zero parameter name length

rsltstring = chkdphone.Substring(chkdphone.Length - 10, 10)

rsltstring = chkdphone.Substring(chkdphone.Length - 10)