Sub NumFeuil()
Dim ws As Worksheet
For Each ws In Worksheets
ws.Range("A1") = ws.Index
Next
End Sub
Option Explicit
Private Sub Workbook_NewSheet(ByVal o As Object)
Dim numéro_onglet As Long
numéro_onglet = ActiveWorkbook.Sheets.Count
[a1] = ActiveWorkbook.Sheets.Count
End Sub