Online user count in asp.net

Hi friends,
I want to get a online user count in asp.net application.
In global.asax i am writing the following codes,
 Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
        Application("ActiveUsers") = 0
    End Sub
   Sub Session_Start(ByVal sender As Object, ByVal e As EventArgs)
        Application.Lock()
        Application("ActiveUsers") = CInt(Application("ActiveUsers")) + 1
        Application.UnLock()
     
    End Sub
  Sub Session_End(ByVal sender As Object, ByVal e As EventArgs)
        Application.Lock()
        Application("ActiveUsers") = CInt(Application("ActiveUsers")) - 1
 &nbs ...