ASP: Write file utf8

Sub LogEvent(message, filename)
    sDate = Now()
 
 'filename
 if filename <> "" then
  filename = filename & "_" & year(sDate)&month(sDate)&day(sDate)
 else
  filename = year(sDate)&month(sDate)&day(sDate)
 end if
 filename = server.mappath(".") & "/log/" & filename
 
 'check file exists
 Set fs = CreateObject("Scripting.FileSystemObject")
 If fs.FileExists(filename) Then
  modeFile = 2
 else
  modeFile = 1
 end if
 set fs = nothing
 
 'write file
 Set objStream = server.CreateObject("ADODB.Stream")
 objStream.Open 
 objStream.CharSet = "UTF-8"
 
 if modeFile = 2 then 
  objStream.LoadFromFile filename
  objStream.ReadText
 end if
 
 objStream.WriteText(sDate & vbTab & message & vbNewLine)

 objStream.SaveToFile filename , modeFile
 objStream.Close
 set objStream = nothing
End Sub

(http://gchandra.wordpress.com/2004/08/19/creating-utf-8-files-using-asp/, http://www.w3schools.com/ado/ado_ref_stream.asp)