VB .NET How do I use the cookies to navigate on the site after login ?

Hi there,
what exactly I want to know is the use of cookies in VB. I am creating a program that login to a website and then let user perform tasks on the site. But I cant make it to navigate on the website, after logging into the website and collecting cookies, when the program navigate to another page the website ask for the login again. How do I use the cookies that I have collected to tell the website that I have just authenticated ?

here are the codes that I am using (assume all the variables are declared globally)

.
.
.
Private Sub loginbtn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles loginbtn.Click
                dim url as system.uri = new system.uri("http://www.somewebsite.com/login.php")
                request = WebRequest.Create(url)
                loginid.Enabled = False
                loginpass.Enabled = False
                loginbtn.Enabled = False
                Me.Text = "Logging in..."
                request.Method = "POST"
                postData = "MobileNoLogin=" + loginid.Text + "&" + "LoginPassword=" + loginpass.Text
                byteArray = Encoding.UTF8.GetBytes(postData)
                request.CookieContainer = cookiejar
                request.ContentLength = byteArray.Length
                request.ContentType = "application/x-www-form-urlencoded"
                request.KeepAlive = True
                dataStream = request.GetRequestStream()
                dataStream.Write(byteArray, 0, byteArray.Length)
                response = request.GetResponse()
                stat = (CType(response, HttpWebResponse).StatusDescription)
                dataStream = response.GetResponseStream()
                reader = New StreamReader(dataStream)
                responseFromServer = reader.ReadToEnd
                messagebox.show(responsefromserver")                [B] '----------->> Shows that I am logged in :)[/B]
                reader.Close()
                dataStream.Flush()
                dataStream.Close()
                response.Close()
End Sub


Private Sub sendbtn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles sendbtn.Click

                ' HERE IT REDIRECT ME TO THE LOGIN PAGE AGAIN :(
        
                request = WebRequest.Create("http://www.website.com/submitmessage.php")
                request.Method = "POST"
                postData = "recepient=somerecepient&Message=Hi, I am testing my application to send messages"
                byteArray = Encoding.UTF8.GetBytes(postData)
                request.CookieContainer = cookiejar
                request.ContentLength = byteArray.Length
                request.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.2.11) Gecko/20101012 Firefox/3.6.11"
                request.ContentType = "application/x-www-form-urlencoded"
                dataStream = request.GetRequestStream()
                dataStream.Write(byteArray, 0, byteArray.Length)
                response = request.GetResponse()
                dataStream.Close()
                stat = (CType(response, HttpWebResponse).StatusDescription)
                dataStream = response.GetResponseStream()
                reader = New StreamReader(dataStream)
                responseFromServer = reader.ReadToEnd
                messagebox.show(responsefromserver)             [B]'--------------> Here I can see the redirection to the login page :([/B]
            Catch ex As Exception
                If ex.ToString.Length <> 0 Then
                    MessageBox.Show(ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error, MessageBoxDefaultButton.Button1, MessageBoxOptions.DefaultDesktopOnly, False)
                    Exit Try
                End If
            End Try
        End If
    End Sub

Code (markup):

Can anybody tell me what I am doing wrong here ? I have the login cookies after successful login but still I cant browse to another page, Please can anybody tell me the right way ?

 

anybody ??
someone please help.