I have my DNS setup to answer for any subdomain.  I need to be able to
look at the URL typed in like "joe.mysite.com" and put the subdomain
in a variable, so I can then look it up in a database. This would have
to work if they typed in http://joe.mysite.com or just joe.mysite.com.

Here is what I have started with, but as you can see I'm a little
stuck.

Sub ExtractDomain(ByVal expr As String)

       Dim sURL As String = Page.Request.Url.ToString()
       Dim subDomain = InStr(1, sURL, "http://")
       If subDomain > 0 Then
           'True so count over 7 characters

       Else
           'False, so start immediately

       End If

   End Sub