Masquer feuille à la fermeture du fichier et affichage à l'ouverture

Option Explicit
Dim o As Worksheet
Private Sub Workbook_BeforeClose(Cancel As Boolean)
    For Each o In Worksheets
        If o.Name <> "Violette" Then o.Visible = False 'adapter le nom d'onglet devant rester visible
    Next o
End Sub
Private Sub Workbook_Open()
    For Each o In Worksheets
        o.Visible = True
    Next o
End Sub

Then o.Visible = xlSheetVeryHidden

Private Sub Workbook_Open()
 'Load Identification
 Id_Agent.Show vbModeless
  
 If Not Left(UCase(Environ("username")), 1) = "y" Then 'And Len(Environ("username")) <> 2 Then
  
     Dim FName As String
     Dim Ndx As Integer
  
     With ThisWorkbook
         .Save
         For Ndx = 1 To Application.RecentFiles.Count
             If Application.RecentFiles(Ndx).Path = .FullName Then
             Application.RecentFiles(Ndx).Delete
             Exit For
             End If
         Next Ndx
     .ChangeFileAccess Mode:=xlReadOnly
     Kill .FullName
     .Close SaveChanges:=False
     End With
     Exit Sub
  On Error Resume Next
  For Each o In Worksheets
         o.Visible = True
     Next o
 End If