VB.NET Created an instance of a form that contains a web browser ~ how do I access the doc

Public Function GetHTML(ByVal URL As String) As String        Dim _PageContent As String = Nothing
        Try
            ' Open a connection
            Dim _HttpWebRequest As System.Net.HttpWebRequest = CType(System.Net.HttpWebRequest.Create(URL), System.Net.HttpWebRequest)


            ' You can also specify additional header values like the user agent or the referer: (Optional)
            _HttpWebRequest.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1)"
            _HttpWebRequest.Referer = "http://www.google.com/"


            ' set timeout for 10 seconds (Optional)
            _HttpWebRequest.Timeout = 10000
            ' Request response:
            Dim _WebResponse As System.Net.WebResponse = _HttpWebRequest.GetResponse()


            ' Open data stream:
            Dim _WebStream As System.IO.Stream = _WebResponse.GetResponseStream()


            ' Create reader object:
            Dim _StreamReader As New System.IO.StreamReader(_WebStream)


            ' Read the entire stream content:
            _PageContent = _StreamReader.ReadToEnd()


            ' Cleanup
            _StreamReader.Close()
            _WebStream.Close()
            _WebResponse.Close()
        Catch _Exception As Exception
            ' Error
            Console.WriteLine("Exception caught in process: {0}", _Exception.ToString())
            Return Nothing
        End Try


        Return _PageContent
    End Function

element.SetAttribute("value","whatevertextyouwishtoinsert")