Sub test()
For i = 1 To Sheets.Count
If Sheets(i).Name <> "Base" Then
If i <> Sheets.Count Then
GoTo suite
Else
MsgBox "La feuille ''Base'' n'existe pas"
End If
Else
MsgBox "la feuille ''Base'' est la feuille n°" & i
Exit For
End If
suite:
Next i
End Sub