Colorer l'aire entre 2 courbes sur graphique en Nuage de points

Sub ColorerDecolorer() 'bouton
If IsError(Application.Caller) Then Exit Sub
With ActiveSheet.DrawingObjects(Application.Caller)
  If .Text Like "Col*" Then
    ColorerAireEntreCourbes
  Else
    Sheets("Source").Range("A4:B" & Rows.Count).Delete xlUp 'conserver 1 point pour la mise en forme
  End If
  .Text = IIf(.Text Like "Col*", "Décolorer", "Colorer") & " l'aire entre les courbes"
End With
End Sub

Sub ColorerAireEntreCourbes()
Dim n&, x1, y1, x2, y2, deb, fin, e, x(), y(), i&, j&, a
n = 2000 'nombre de points
x1 = [X_1]: y1 = [Y_1]: x2 = [X_2]: y2 = [Y_2]
deb = Application.Max(Application.Min(x1), Application.Min(x2))
fin = Application.Min(Application.Max(x1), Application.Max(x2))
e = (fin - deb) / n
ReDim x(1 To n + 1, 1 To 1): ReDim y(1 To n + 1, 1 To 1)
For i = 1 To n Step 2
  x(i, 1) = deb + (i - 1) * e
  x(i + 1, 1) = x(i, 1)
  j = Application.Match(x(i, 1), x1)
  a = (y1(j + 1, 1) - y1(j, 1)) / (x1(j + 1, 1) - x1(j, 1))
  y(i, 1) = y1(j, 1) + a * (x(i, 1) - x1(j, 1))
  j = Application.Match(x(i, 1), x2)
  a = (y2(j + 1, 1) - y2(j, 1)) / (x2(j + 1, 1) - x2(j, 1))
  y(i + 1, 1) = y2(j, 1) + a * (x(i, 1) - x2(j, 1))
Next
With Sheets("Source").[A3].Resize(n)
  .Value = x
  .Name = "X"
End With
With Sheets("Source").[B3].Resize(n)
  .Value = y
  .Name = "Y"
End With
End Sub