VB.NET: Automatic login to .NET website.

Im from Australia and i'm trying to create an app that will login to Australia's TAB website (tab.com.au) and place a bet. The website seems to be have been created in ASP.NET but there is a lot of javascript and i can't work out how i should go about this..
I know how to transmit and receive the http headers but am not sure what needs to be sent and receive (as it is a fairly complex and secure system).
I've used an Http packet sniffer to see what headers the browser is sending and receiving and still can't seem to work it out... does anyone have any ideas or is there is anyone who has done something similar?

I did manage to login and place a bet using the WebBrowser control by filling in the textboxes with code and then creating a 'click' event on the login button, but when it submits the bet it only works sometimes and otherwise comes up with a 'Server error'... i have no idea why this happens, my only guess is that it does that when there is too many requests from the same IP (within a specific timeframe) and it blocks that IP for a certain amount of time (as i found yahoo search does).

Any advice would be appreciated.
Here is the code i am currently using.. it may be of use to someone:

Dim whereami as Integer
Dim loggedin as Boolean

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        whereami = 0
        loggedin = False
        WebBrowser1.Navigate("http://www.tab.com.au/racing/default.aspx?State=1")
    End Sub

    Private Sub WebBrowser1_DocumentCompleted(ByVal sender As System.Object, ByVal e As System.Windows.Forms.WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
        If whereami = 0 Then
            Dim but1 As Object
            WebBrowser1.Document.GetElementById("DisplayTopMenu_DisplayTopNav1_TextboxLogin").SetAttribute("value", "123456")
            WebBrowser1.Document.GetElementById("DisplayTopMenu_DisplayTopNav1_TextboxPassword").SetAttribute("value", "mypassword")
            but1 = WebBrowser1.Document.GetElementById("DisplayTopMenu_DisplayTopNav1_ButtonLogin").DomElement
            but1.Click()
            whereami = whereami + 1
            Exit Sub
        ElseIf whereami = 1 Then
            WebBrowser1.Navigate("http://www.tab.com.au/ExpressBet/Standard/Default.aspx?State=1")
            whereami = whereami + 1
            Exit Sub
        ElseIf whereami = 2 Then
            Dim dom As Object
            dom = WebBrowser1.Document.DomDocument
            dom.Links(1).Click()
            whereami = whereami + 1
            loggedin = True
            Exit Sub
        End If
    End Sub

    Sub placebets(ByVal batchbets As String)
        Dim olddate As Date
        Dim procs() As Process
        WebBrowser1.Document.GetElementById("BvTextArea").InnerText = batchbets
        ClickLink(WebBrowser1.Document.DomDocument, "SUBMIT BATCH")
        olddate = Now
'Wait five seconds until the confirmation window opens
        Do
            Application.DoEvents()
        Loop Until DateDiff(DateInterval.Second, olddate, Now) >= 5 Or DateDiff(DateInterval.Second, olddate, Now) <= -5
        procs = Process.GetProcesses()
'close confirmation window
        For i = 0 To procs.Length - 1
            If procs(i).MainWindowTitle = "https://www.tab.com.au/?State=1 - BetReceiptSummary - Windows Internet Explorer" Then
                procs(i).CloseMainWindow()
                Exit For
            End If
        Next
    End Sub

    Sub ClickLink(ByVal doc As Object, ByVal LinkText As String)
        For i = 0 To doc.Links.Length - 1
            If LTrim(RTrim(doc.Links(i).OuterText)) = LinkText Then
                doc.Links(i).Click()
                Exit For
            End If
        Next i
    End Sub

Code (markup):

If you use the Aus TAB website, this will probably make sense to you more then most people, but you can use code similar to this to login to any website. If it isn't obvious WebBrowser1 is a webbrowser control.

Any advice on why i may get the 'server error' or how to do this using only HTTP Requests, please let me know..

 

If the IP is getting problems due to too many requests, I'm not sure that HTTP requests will be any better.

One thing that might be affecting your code is the state of the webbrowser control. Read this webbrowser documentcompleted info to find out more. Sorry not to be of more help.

 

it isn't the webbrowser itself.. when a bet is placed a confirmation window is launched. This window most of the time displays 'Server Error'.. i might have to try it again, maybe there was an actual error on the server when i was testing it, or i tested it too much, which blocked me. I know yahoo says the same thing when you post too many requests too quickly.

But i would prefer to use direct requests as opposed to webbrowser...

 

That link is interesting... i have no problem with the code executing, just with the server response..

 

I realize this is over a year old, but I wondered if you ever found a solution?
I'm using similar code to your sample, but C# - the problem seems to be when the connection tries to switch from http to https.
I discovered if I open up IE manually and logon there, my program is able to make the SSL connection to submit bets, but of not, it just hangs, and then times out.
Did you ever solve this?
Would be very grateful for some clues if you did, or to bounce some ideas around if you are still interested in solve this yourself ;-)

Thanks!