Public Class Form1
    Dim su As Stopwatch = New System.Diagnostics.Stopwatch
    Sub M10Timer()
        Console.Beep(1000, 20)
    End Sub
    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Timer1.Tick
        If su.Elapsed.TotalSeconds >= 10 Then           ' If 
        ' su.Elapsed.TotalMinutes >= 10 Then
            su.Reset()
            su.Start()
            M10Timer()
        End If
        TextBox1.Text = su.Elapsed.ToString.Substring(3, 5)
    End Sub
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Timer1.Interval = 1000
        Timer1.Start()
        su.Start()
    End Sub
End Class