Ciao x69asterix !
Basta impostare Orientation = rptOrientLandscape, così:
codice:
'Imposta i margini del Report:
    With Me
    .Orientation = rptOrientLandscape
    .TopMargin = 720
    .BottomMargin = 1440
    .LeftMargin = 100
    .RightMargin = 100
    .ReportWidth = 11400
'Imposta larghezza del Report:
        If Me.WindowState = vbNormal Then
        .Width = Screen.Width    
        .Height = Screen.Height
        .Left = (Screen.Width - .Width) / 2
        .Top = (Screen.Height - .Height) / 2
        End If
    End With