empêcher d'avoir cellule vide

Const Zone = "b2:b12"

Private Sub Worksheet_Change(ByVal Target As Range)
Dim elem, Pasok As Boolean, Plage As Range

   On Error GoTo ERR01
   Set Plage = Intersect(Me.Range(Zone), Target)
   If Not Plage Is Nothing Then
      For Each elem In Plage
         If Not IsNumeric(elem) Or elem = "" Then
            Pasok = True
         ElseIf elem < 0 Then
            Pasok = True
         End If
      Next elem
      If Pasok Then
         Beep
         Application.EnableEvents = False
         Application.Undo
         Application.EnableEvents = True
      End If
   End If

ERR01:
   Application.EnableEvents = True
End Sub