Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        'berekenen timer
        Timer1.Enabled = False
        Dim timetogo As String() = TimeString.Split(":")
        If timetogo(1) > 30 Then
            timetogo(1) = timetogo(1) - 30
            Timer2.Interval = (1800000 - (timetogo(1) * 60 + timetogo(2)) * 1000)
            Timer2.Enabled = True
        End If
    End Sub


    Private Sub timer2_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        Timer1.Enabled = True
    End Sub