VS 2010 Make A Program That Scans A Website For The Forum Directory?

Ive been trying to make a program that scans a website for the Forum directory mainly to learn about HttpWebRequest.I know that i need the url, and the request, so i set that up like this:

Dim Message As String = String.Empty
Dim request As HttpWebRequest = DirectCast(HttpWebRequest.Create(Url), HttpWebRequest)

and i set the Credentials to DefaultCredentials Now, How would i scan the directories?

i've tried

for response as HttpWebResponse = DirectCast(request.GetResponse(), HttpWebResponse)
logBox.Text = logBox.Text & vbNewLine & response.ToString()
next

but this has errors...Just trying to scan a site for multiple directories using HttpWebRequest.