incompatibilité de type sur plage de cellules

Private Sub Worksheet_Change(ByVal Modif As Range)
Dim x As Integer, y As Integer, z As Integer
Dim e As String, f As String
Dim d3 As Date, d4 As Date
Dim Cellule As Range
Dim toto As Range
x = Modif.Row
d3 = Cells(x, 4).Value
d4 = Cells(x, 6).Value

If d3 = 0 Or d4 = 0 Then
Exit Sub
Else
    For y = 6 To 400
        If Worksheets("Quanti").Cells(y, 3).Value = d3 Then
            e = Worksheets("Quanti").Cells(y, 3).Address
        End If
        If Worksheets("Quanti").Cells(y, 3).Value = d4 Then
            f = Worksheets("Quanti").Cells(y, 3).Address
        End If
    Next
    new_plage = Worksheets("Quanti").Range(e, f).Address
    MsgBox (new_plage)
End If

For z = 5 To 65
    If Worksheets("Quanti").Cells(2, z).Value = Cells(x, 1).Value Then
        [COLOR="Red"]For Each Cellule In old_plage[/COLOR]
            If Not Intersect(Cellule, new_plage) Is Nothing Then
                Cellule.Offset(0, z - 3).Value = "0"
            End If
        Next Cellule
        For Each Cellule In new_plage
            If Cells(x, 5).Value = "Matin" Then
                Cellule.Offset(0, z - 3).Value = "1"
            Else:
                Cellule.Offset(0, z - 3).Value = "0,5"
            End If
            If Cells(x, 7).Value = "Matin" Then
                Cellule.Offset(0, z - 3).Value = "0,5"
            Else:
                Cellule.Offset(0, z - 3).Value = "1"
            End If
        Next
    End If
Next

End Sub

Public old_plage, new_plage
Option Explicit

Sub Worksheet_SelectionChange(ByVal Sel As Range)
...
Private Sub Worksheet_Change(ByVal Modif As Range)
...