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_OnResolveRequestCache()
  
    Response.Write("served from cache...<hr size=1>")
  
  End Sub


  Public Sub Application_OnUpdateRequestCache()
  
    WriteLog("Updating cache...")
    
  End Sub
  
  Private Sub WriteLog(message As String)
  
    Dim logname As String = "Web_Errors"

    If Not EventLog.SourceExists(logname) Then
      EventLog.CreateEventSource(logname, logname)
    End If

    Dim l As New EventLog()
    l.Source = logname
    l.WriteEntry(message, EventLogEntryType.Information)
  
  End Sub
  
</Script>