Imports System.Threading

Public Class frmMain

    Private stopWatch As New Stopwatch()
    Private beeper As Threading.Thread
    Private beep As Threading.Thread

    Private Sub beepCycler()
        stopWatch.Start()
        While (True)
            Thread.Sleep(0)
            If stopWatch.Elapsed.Milliseconds > 100 Then
                beep = New Threading.Thread(AddressOf doBeep)
                beep.Start()
                stopWatch.Stop()
                stopWatch.Start()
            End If
        End While
    End Sub

    Private Sub btnStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStart.Click
        If btnStart.Text = "Start" Then
            btnStart.Text = "Stop"
            beeper = New Threading.Thread(AddressOf beepCycler)
            beeper.Start()
        Else
            btnStart.Text = "Start"
            Try
                beeper.Abort()
            Catch ex As Exception
                '
            End Try

        End If

    End Sub

    Private Sub doBeep()
        Console.Beep(310, 200)
    End Sub

End Class