Sub test()
strVal = Format(Application.Round([O1] / [K1], 2), "0.00%") & Chr(10) & "( // Comptes arrêtés)"
pos = InStr(strVal, "(")
ActiveCell = strVal
ActiveCell.Characters(Start:=pos, Length:=21).Font.Superscript = True
ActiveCell.ColumnWidth = 14
End Sub