HttpWebRequest and ViewState Issue

[Stumped]

I'm trying to remotely logon to a website however I'm experiencing a view state problem, due to there being a web cluster in place.

I currently create an HttpWebRequest to GET login page, I then obtain the ViewState and EventValidation values from the response and then create another HttpWebRequest to POST those back with my login details. The problem is I can't be sure I'll be posting back to the same box that provided me with the ViewState value.

I've tried to post the logon details without a ViewState or EventValidation value but with no joy, the response is simply the login page.

Is there a property on the WebRequest I should be setting or am I missing something quite basic here? I have the following set


Dim req As HttpWebRequest = CType(WebRequest.Create(URL), HttpWebRequest)
Dim cache As New Cache.HttpRequestCachePolicy(Net.Cache.HttpRequest CacheLevel.NoCacheNoStore)
With req
.Method = "POST"
.ContentType = "application/x-www-form-urlencoded"
.ContentLength = datalen
.UserAgent = "MSIE 7.0"
.ProtocolVersion = HttpVersion.Version10
.KeepAlive = True
.Referer = URL
.CachePolicy = cache
End With

[Stumped]

Sorted

Thanks anyway