Visual Basic.NET - ayuda con error

Private Sub mtxRut_Validated(ByVal sender As Object, ByVal e As System.EventArgs) Handles mtxRut.Validated

        Dim rutLimpio As String

        Dim digitoVerificador As String

        Dim suma As Integer

        Dim contador As Integer = 2

        rutLimpio = mtxRut.Text.Replace(".", "")

        rutLimpio = rutLimpio.Replace("-", "")

        rutLimpio = rutLimpio.Replace(" ", "")

        rutLimpio = rutLimpio.Substring(0, rutLimpio.Length - 1)

        digitoVerificador = mtxRut.Text.Substring(mtxRut.Text.Length - 1, 1)

        Dim i As Integer

        For i = rutLimpio.Length - 1 To 0 Step -1

            If contador > 7 Then

                contador = 2

            End If

            suma += Integer.Parse(rutLimpio(i).ToString()) * contador

            contador += 1

        Next

        Dim dv As Integer = 11 - (suma Mod 11)

        Dim DigVer As String = dv.ToString()

        If DigVer = "10″ Then" Then

            DigVer = "K"

        End If

        If DigVer = "11″ Then" Then

            DigVer = "0″"

        End If

        If DigVer = digitoVerificador.ToUpper Then

            lbRut.Text = "Rut Valido"

            txtNombreEmp.Focus()

            btIngresarEmp.Enabled = True

        Else

            lbRut.Text = "Rut Invalido"

            MessageBox.Show("Rut Invalido", "Aviso", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)

            mtxRut.Focus()

            mtxRut.SelectAll()

            btIngresarEmp.Enabled = False

        End If

    End Sub