Here's a simple ASP.NET function that will get the opposite result of the Server.MapPath() function. This comes in handy when you're retrieving files recently saved by your web application. Pass it a fully qualified path and it returns a URL
Public Function MapURL(ByVal Path As String) As String
Dim AppPath As String = _
HttpContext.Current.Server.MapPath("~")
Dim url As String = String.Format("~{0}" _
, Path.Replace(AppPath, "").Replace("\", "/"))
Return url
End Function
Of course, you will have to make sure that the path is valid and the file is under the virtual root.
Enjoy!