Sub AjoutFeuilles()
Dim Cel As Range, DerLig As Long, NomSht As String
Dim Sht As Worksheet
' Mise à jour des variables
Set Sht = Sheets("Feuil1")
DerLig = Sht.Range("A" & Rows.Count).End(xlUp).Row
For Each Cel In Sht.Range("A2:A" & DerLig)
On Error Resume Next
' Provoque une erreur si feuille inexistante
Sheets(Cel.Value).Activate
'
If Err.Number <> 0 Then
Sheets("Janvier").Copy After:=Sheets(Sheets.Count)
ActiveSheet.Name = Cel
End If
Next Cel
Set Sht = Nothing
End Sub