Excel 2007 VBA-Nom user ?

Option Explicit 
Const fichier As String = "D:\documents\bigbrother.txt" 'A ADAPTER AU CONTEXTE 
Private Declare Function GetUserName Lib "advapi32.dll" Alias "GetUserNameA" _ 
(ByVal lpBuffer As String, _ 
nSize As Long) As Long 

'A partir d'une démo de @+Thierry  
Private Sub Workbook_Open() 
Dim lpBuff As String * 25 
Dim retour As Long 
Dim utilisateur As String, cafte As String 

retour = GetUserName(lpBuff, 25) 
utilisateur = Left(lpBuff, InStr(lpBuff, Chr(0)) - 1) 

cafte = "Ouvert à : " & Format(Now, "dd/mm/yyyy hh:mm:ss") & _ 
vbTab & "par : " & utilisateur 

Open fichier For Append As #1 
Print #1, cafte 
Close 

End Sub 

Private Sub Workbook_BeforeClose(Cancel As Boolean) 
Dim lpBuff As String * 25 
Dim retour As Long 
Dim utilisateur As String, cafte As String 

retour = GetUserName(lpBuff, 25) 
utilisateur = Left(lpBuff, InStr(lpBuff, Chr(0)) - 1) 

cafte = "Fermé à  : " & Format(Now, "dd/mm/yyyy hh:mm:ss") & _ 
vbTab & "par : " & utilisateur 

Open fichier For Append As #1 
Print #1, cafte 
Close 

End Sub