global.asax

This is a book about vb.you could learn this from this book

<%@ Import Namespace="System.Diagnostics" %>

<script language="VB" runat=server>
  Public Sub Application_Error(Sender as Object, E as EventArgs)

    Dim LogName As String = "Web_Errors"
    Dim Message As String
    Message = "Url: " & Request.Path
    Message = Message + " Error: " & Server.GetLastError.ToString

    ' Create Event Log if It Doesn抰 Exist
    If (Not EventLog.SourceExists(LogName)) Then
      EventLog.CreateEventSource(LogName, LogName)
    End if

    ' Fire off to Event Log
    Dim Log as New EventLog

    Log.Source = LogName
    Log.WriteEntry(Message, EventLogEntryType.Error)

  End Sub
</script>