Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As _
  System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        If Not ((System.Convert.ToInt32(e.KeyChar) >= 65 AndAlso _
        System.Convert.ToInt32(e.KeyChar) <= 90) OrElse _
           (System.Convert.ToInt32(e.KeyChar) >= 97 AndAlso _
           System.Convert.ToInt32(e.KeyChar) <= 122)) Then
            e.Handled = True
        End If
    End Sub