Sub creation_page()
Dim NomFeuille As String, Test As Boolean, Ws As Worksheet
NomFeuille = Sheets("Feuil1").Range("F5").Value
For Each Ws In Worksheets
If Ws.Name = NomFeuille Then Test = True: Exit For
Next Ws
If Test Then
MsgBox "Cette feuille existe déjà !"
Else
Sheets("modele").Copy After:=Sheets(Sheets.Count)
ActiveSheet.Name = NomFeuille
End If
End Sub