Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
For i = 1 To Sheets.Count
If (Sheets(i).Name <> "Intro" Or Sheets(i).Name <> "Synthèse") And Sheets(i).[A1] = True And Sheets(i).[B20] = "" Then
MsgBox ("La cellule B20 de la feuillle " & Sheets(i).Name & " ne peut être vide")
Cancel = True
Exit Sub
End If
Next i
End Sub