Control puerto serial visual 2008

Imports System.IO.Ports
Imports System.Windows.Forms
Public Class Form1
Dim vector() As String
Dim contador As Integer
Dim combo As New ComboBox
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
combo.Items.AddRange(SerialPort.GetPortNames)
If combo.Items.Count > 1 Then
SerialPort1.PortName = combo.Items.Item(1)
SerialPort1.Open()
If SerialPort1.IsOpen Then
Timer1.Enabled = True
End If
End If
End Sub

Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
Try
SerialPort1.Write(TextBox1.Text)
Label1.Text = SerialPort1.ReadExisting
Catch ex As Exception

End Try
End Sub
End Class