[2005] Determine if authenticated?

Is there a way of determining whether a download request was successful? e.g.

VB Code:

Try
    My.Computer.Network.DownloadFile(folder, f, Username, Password, False, 10000, True)
Catch
    'Does not jump here on bad authentication
End Try

This does not throw an exception if the username and password do not match the sites (basic) authentication requirement. I have the same problem if I use a WebClient.