Private Sub Worksheet_Change(ByVal Target As Range)
Sheets("Synthèse").Unprotect
If Target.Address <> "$C$28" Then Exit Sub
For n = 1 To 10: Sheets(CStr(n)).Visible = n < Target + 1: Next
Sheets("Synthèse").Rows("3:26").Hidden = 0
If Target < 10 Then Sheets("Synthèse").Rows(9 + 2 * (Target - 1) & ":26").Hidden = Target
Sheets("Synthèse").Protect
End Sub