Extract cookie from browser and attach to WebRequest

Question

I have the following code to send a WebRequest to Betfair, usually this would be sent from a browser and it would send cookie data with it to identify my login, how would I go about attaching the cookie data to this request? (I need to find out how to extract the cookie data first, if anyone can point to any useful articles relating to that it would be much appreciated).

   Private Sub Place_Bet(ByVal marketId As String, selectionId As String)

    Dim url As Uri
    url = New Uri("https://etx.betfair.com/www/etx-json-rpc?_ak=nzIFcwyWhrlwYMrh&alt=json")
    Dim json As String = "[{""method"":""ExchangeTransactional/v1.0/place....}]"
    Dim data = Encoding.UTF8.GetBytes(json)
    Dim result_post = SendRequest(url, data, "application/json", "POST")

    MsgBox(result_post)
End Sub

Private Function SendRequest(uri As Uri, jsonDataBytes As Byte(), contentType As String, method As String) As String
    Dim response As String
    Dim request As WebRequest

    request = WebRequest.Create(uri)
    request.ContentLength = jsonDataBytes.Length
    request.ContentType = contentType
    request.Method = method

    Using requestStream = request.GetRequestStream
        requestStream.Write(jsonDataBytes, 0, jsonDataBytes.Length)
        requestStream.Close()

        Using responseStream = request.GetResponse.GetResponseStream
            Using reader As New StreamReader(responseStream)
                response = reader.ReadToEnd()
            End Using
        End Using
    End Using

    Return response
End Function