I finally got the solution from msdn after series of research work. Here is the solution in case it might help other people:
Private Sub callbk()
Threading.Thread.Abort()
End Sub
Private Sub btn_start(ByVal sender As Object, ByVal e As System.EventArgs) Handles btn_start.Click
Dim tcb As TimerCallback = AddressOf callbk
Dim t As Timer = New Timer(tcb, Nothing, 5000, -1)
While True
End While
End Sub
thanks!