Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles Button1.Click
        TrackBar1.Value = 3
        Timer1.Interval = 1000 '1000ms = 1s
End Sub
 
 
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles Timer1.Tick
        Timer1.Enabled = False
        TrackBar1.Value = 8
End Sub