Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
Dim debut As Range, a, i
Set debut = Feuil1.Cells(1) 'CodeName de la feuille à adapter
If Not IsNumeric(CStr(debut)) Then debut = 0
a = Array("lundi", "mardi", "mercredi", "jeudi", "vendredi", "samedi")
Application.EnableEvents = False
On Error Resume Next 'sécurité
For i = 0 To 5
Sheets(a(i)).Cells(1) = debut + i + 1
Next
Application.EnableEvents = True
End Sub