Function NomExiste(nom$) As Boolean
Application.Volatile
Dim n As Name
On Error Resume Next
Set n = ThisWorkbook.Names(nom)
NomExiste = Not n Is Nothing
End Function
Function FeuilleExiste(nom$) As Boolean
Application.Volatile
Dim s As Object
On Error Resume Next
Set s = Sheets(nom)
FeuilleExiste = Not s Is Nothing
End Function