HTTP Web Request - vb.net

Question

I am halfway done with this project. I need to login to my server at work, then submit a form on a different page. How do I keep the login connection alive then post a second form, or url?
Dim postData As String = "Username=system&Password=system&Action=Srh-1-1&Go=Login"
Dim tempCookies As New CookieContainer
Dim encoding As New UTF8Encoding
Dim byteData As Byte() = encoding.GetBytes(postData)
Dim postReq As HttpWebRequest = DirectCast(WebRequest.Create("MY SERVER URL"), HttpWebRequest)
postReq.Method = "POST"
postReq.KeepAlive = True
postReq.CookieContainer = tempCookies
postReq.ContentType = "application/x-www-form-urlencoded"
postReq.Referer = "MY SERVER URL"
postReq.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.1; ru; rv:1.9.2.3) Gecko/20100401 Firefox/4.0 (.NET CLR 3.5.30729)"
postReq.ContentLength = byteData.Length
Dim postreqstream As Stream = postReq.GetRequestStream()
postreqstream.Write(byteData, 0, byteData.Length)
postreqstream.Close()
Dim postresponse As HttpWebResponse
postresponse = DirectCast(postReq.GetResponse(), HttpWebResponse)
tempCookies.Add(postresponse.Cookies)
'logincookie = tempCookies
Dim postreqreader As New StreamReader(postresponse.GetResponseStream())
Dim thepage As String = postreqreader.ReadToEnd
RichTextBox1.Text = thepage
So, the login works fine. But, again, how do i now post to a different form, or load the entire form + submission details into a url? I need to post data after being logged in and submit the form. The form will return data I will then parse out. Basically, all of this can be done manually but this program will save me time by logging in, submitting, and parsing automatically.