How to show Hour:Minute:Second:Milisecond in Stopwatch using VB.NET?

Public Class Form1
    Dim running As Boolean = False
    Dim miliSeconds As Integer = 0, seconds As Integer = 0, minutes As Integer = 0, hours As Integer = 0
    Dim startTime As DateTime
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        startTime = DateTime.Now
        running = True
        Timer1.Enabled = True
        Timer1.Start()
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        running = False
        Timer1.Stop()
        Timer1.Enabled = False
    End Sub

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick

        'miliSeconds += 1
        'If miliSeconds = 1000 Then
        '    miliSeconds = 0
        '    seconds += 1
        '    If (seconds = 60) Then
        '        seconds = 0
        '        minutes += 1
        '        If (minutes = 60) Then
        '            minutes = 0
        '            hours += 1
        '        End If
        '    End If
        'End If
        'Label1.Text = hours & ":" & minutes & ":" & seconds & ":" & miliSeconds
        Dim diff As TimeSpan = DateTime.Now - startTime
        Label1.Text = diff.ToString("hh\:mm\:ss\:fff")

    End Sub


End Class