using credentials

[Scot]

I have this currently:

Public Function GetPageHTML( _
ByVal URL As String) As String
' Retrieves the HTML from the specified URL
Dim objWC As New System.Net.WebClient

Dim myCredentials As New System.Net.NetworkCredential("myusername",
"mypassword")
objWC.Credentials = myCredentials

Return New System.Text.UTF8Encoding().GetString( _
objWC.DownloadData(URL))
End Function
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Dim strHTML As String
strHTML = GetPageHTML("http://my.yahoo.com")
TextBox1.Text = strHTML
End Sub

All it seems to do is give me the default page to my.yahoo.com, if I put a
URL that is further in, it kicks me back and says you didn't login. Am I
using the NetworkCredentials improperly? Can someone steer me in the right
direction on this?

Thanks,

Scott