Public valeurA1 As Variant
Private Sub Worksheet_Activate()
valeurA1 = Range('A1')
End Sub
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address = '$A$1' Then
If Target.Value - valeurA1 > 100 Then
reponse = MsgBox(' Attention + de 100' & Chr(10) & 'voulez-vous confirmer', vbYesNo)
If reponse = vbYes Then
valeurA1 = Range('A1')
Else
Range('A1').Value = valeurA1
Me.Activate
End If
End If
valeurA1 = Range('A1')
End If
End Sub