How can i make user writes only character in a textbox

Question

i try this but it dosen't work
 

Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged

        Dim x As String = Nothing

        If TextBox1.TextLength > 0 Then

            For j As Integer = 0 To TextBox1.Text.Count - 1

                If Char.IsNumber(TextBox1.Text(j)) Or Char.IsSymbol(TextBox1.Text(j)) Then

                    t = j

                    Dim s As String() = Split(TextBox1.Text, TextBox1.Text(j))

                    For i As Integer = 0 To s.Count - 1

                        x = x & s(i)

                    Next

                    TextBox1.Text = x

                    Exit Sub

                End If

            Next

        End If

    End Sub