'Dans le module ThisWorkbook de l'application :
'(Laurent Longre)
Private Declare Function FindWindowA Lib "User32" _
(ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function GetWindowLongA Lib "User32" _
(ByVal hwnd As Long, ByVal nIndex As Long) As Long
Private Declare Function SetWindowLongA Lib "User32" _
(ByVal hwnd As Long, ByVal nIndex As Long, _
ByVal dwNewLong As Long) As Long
Private Sub Workbook_BeforeClose(Cancel As Boolean)
Dim hwnd As Long
hwnd = FindWindowA(vbNullString, Application.Caption)
SetWindowLongA hwnd, -16, GetWindowLongA(hwnd, -16) Or &H80000
End Sub
Private Sub Workbook_Open()
Dim hwnd As Long
hwnd = FindWindowA(vbNullString, Application.Caption)
SetWindowLongA hwnd, -16, GetWindowLongA(hwnd, -16) And &HFFF7FFFF
End Sub