Private index As Integer
 
Private Sub TextBox_KeyUp(ByVal sender As Object, ByVal e As _
  System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyUp, TextBox2.KeyUp, _
  TextBox3.KeyUp
        Dim tb As TextBox = CType(sender, TextBox)
        tb.CharacterCasing = CharacterCasing.Upper
        If tb.TextLength = 2 And tb.Text <> "XX" Then 
            Me.Controls("TextBox" & index.ToString) .Focus()
            index += 1
        End If
    End Sub