Problème définition d’une zone d’impression

Option Explicit

Private Sub Impression_A4_Click()
Dim DerLig As Long, i As Long, aff As Worksheet
'Impression au format A4
Set aff = Sheets("affectation")
With aff
    DerLig = .Cells.Find("*", , , , xlByRows, xlPrevious).Row
    .DisplayAutomaticPageBreaks = False
    For i = 28 To DerLig Step 23 'Saut de page après 28 lignes
        .HPageBreaks.Add before:=Rows(i + 1)
    Next i
    With .PageSetup
                  .PrintTitleRows = "$A$1:$F$5"             'Copie 5 lignes sur chaque page
                  .PrintArea = "A1:F" & DerLig              'Impression jusqu’à dernière ligne
                  .PaperSize = xlPaperA4                    'Format A4
                  .Orientation = xlPortrait                 'Impression portrait
                  .LeftMargin = Application.InchesToPoints(0.25)        'définition des marges
                  .RightMargin = Application.InchesToPoints(0.25)
                  .TopMargin = Application.InchesToPoints(0.25)
                  .BottomMargin = Application.InchesToPoints(0.25)
                  .Zoom = False
                  .FitToPagesWide = 1                   'adaptation largeur feuille
         End With
       .PrintPreview
End With
End Sub