Public Function GetVal_on_closed_fich(ByVal chemin As String, ByVal fichier As String, ByVal feuille As String, cel As String) As Variant
Dim Rc$
MsgBox cel
Rc = "R" & Range(cel).Row & "C" & Range(cel).Column
GetVal_on_closed_fich = ExecuteExcel4Macro("'" & chemin & "\[" & fichier & "]" & feuille & "'!" & Rc)
End Function
Sub test()
MsgBox GetVal_on_closed_fich("C:\Users\polux\DeskTop\", "cible.xlsx", "Feuil1", [B4].Value)
End Sub