Sub CreerAvenant()
Dim s As Object, n%, maxi%, F As Object
For Each s In Sheets
If s.Name Like "avenant*" Then
n = Val(Replace(s.Name, "avenant", ""))
If n >= maxi Then
maxi = n
Set F = s
End If
End If
Next
If F.Index < Sheets.Count Then F.Move After:=Sheets(Sheets.Count)
Sheets("avenant").Copy After:=F
ActiveSheet.Name = "avenant" & " " & maxi + 1
End Sub