How can i make user writes only character in a textbox

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)

TextBox1.Text = x

Exit Sub

End If

End Sub