how to make a countdown ?

[xfrolox]

Well im trying to make a countdown
but i need a little help in here.

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Timer1.Interval = 500
        Timer1.Start()
    End Sub
    Dim stpw As New Stopwatch
    Dim CountDownFrom As Integer = 60 * 60
    Dim CountDown As New TimeSpan
    Private Sub StartCountDown()
        CountDown = TimeSpan.FromSeconds(CountDownFrom)
        stpw.Stop() : stpw.Reset() : stpw.Start()
    End Sub
    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        If Not stpw.IsRunning Then Exit Sub
        Dim TimeRemaining As TimeSpan = CountDown - stpw.Elapsed
        TextBox1.Text = TimeRemaining.Hours.ToString.PadLeft(2, "0"c) & ":" & _
                        TimeRemaining.Minutes.ToString.PadLeft(2, "0"c) & ":" & _
                        TimeRemaining.Seconds.ToString.PadLeft(2, "0"c)
        If TimeRemaining.TotalMilliseconds <= 0 Then stpw.Stop()
    End Sub
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        StartCountDown()
        Timer1.Start()
    End Sub

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

it only countdown by the

Dim CountDownFrom As Integer = 60 * 60

i would like to put like
Button3 give the integer of 60 min that is 60 * 60

and button4 give the integer 30 * 60
so

TextBox1 is blank i click button 3 should put 00:60:00
and if button4 is clicked too it should add 30 min more wold be
01:30:00

help please this is 2 much for me :(