using data received events

Hi forum

I am not sure how to use data received events from this code I given.. Can you help me please.I dont know where to put the data received events.

Imports System.IO
Imports System.IO.Ports
Imports System.Threading
Imports System.Data
Imports System.Text


Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs)
        SerialPort1.Close()
        SerialPort1.PortName = "com4" 'change com port to match your Arduino port
        SerialPort1.BaudRate = 9600
        SerialPort1.DataBits = 8
        SerialPort1.Parity = Parity.None
        SerialPort1.StopBits = StopBits.One
        SerialPort1.Handshake = Handshake.None
        SerialPort1.Encoding = System.Text.Encoding.Default 'very important!


    End Sub
 

    Private Sub Start_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Start.Click

        Dim SP As String
        Dim FB As Integer
        Dim A As Integer

        SP = TextBox1.Text
        FB = CInt(Label2.Text)
        A = SP - FB
        Label3.Text = A

        SerialPort1.Open()
        SerialPort1.Write(A)

    End Sub



    Private Sub Timer1_Tick(ByVal sender As Object, ByVal e As EventArgs)
        Dim s As String
        Try
            s = SerialPort1.ReadExisting()
            Label2.Text = s
        Catch ex As Exception

        End Try
    End Sub






End Class