not understanding prtdevmode example

I would like to change the papersize of the report from 8.5 X 11 to 6X4 .  I've used the following example and I don't seem to understand it.
when I run this example and select change paper size the inputboxes come up for width and length.  then the report tries to open and the error
"there was a problem retrieving printer information for the HP printer.  the object may have been sent to a printer that is unavailable."

What is going on and how do I change the size of the report in code?

Option Explicit

       Type zwtDevModeStr
        RGB As String * 94
      End Type

      Type zwtDeviceMode
        dmDeviceName As String * 16
        dmSpecVersion As Integer
        dmDriverVersion As Integer
        dmSize As Integer
        dmDriverExtra As Integer
        dmFields As Long
        dmOrientation As Integer
        dmPaperSize As Integer
        dmPaperlength As Integer
        dmPaperWidth As Integer
        dmScale As Integer
        dmCopies As Integer
        dmDefaultSource As Integer
        dmPrintQuality As Integer
        dmColor As Integer
        dmDuplex As Integer
        dmResolution As Integer
        dmTTOption As Integer
        dmCollate As Integer
        dmFormName As String * 16
        dmPad As Long
        dmBits As Long
        dmPW As Long
        dmDFI As Long
        dmDRr As Long
      End Type




 Sub CheckCustomPage(rptName As String)
         ' The zwtDevModeStr and zwtDeviceMode types are defined in the
         ' zwAllGlobals module in the WZFRMRPT.MDA file.
         Dim DevString As zwtDevModeStr
         Dim DM As zwtDeviceMode
         'Constants for the Fields member.
         Const DM_PAPERSIZE = &H2
         Const DM_PAPERLENGTH = &H4
         Const DM_PAPERWIDTH = &H8
         Dim DevModeExtra As String
         Dim rpt As Report
         Dim response
         Dim msg As String
         'Open the report in Design view.
         DoCmd.OpenReport rptName, acViewDesign
         'DoCmd OpenReport rptName, A_DESIGN (in Microsoft Access 2.0)
         Set rpt = Reports(rptName)
         If Not IsNull(rpt.PrtDevMode) Then
            'Copy the PrtDevMode property to a string.
            DevModeExtra = rpt.PrtDevMode
            DevString.RGB = DevModeExtra
            LSet DM = DevString
            'Check for the custom page size.
            If DM.dmPaperSize = 256 Then
               'Display the custom page size.
               msg = "The Custom Page Size is " & DM.dmPaperWidth / 254
               msg = msg & " inches wide by " & DM.dmPaperlength / 254
               msg = msg & " inches long. Change the size?"
               response = MsgBox(msg, 4)
            Else
               msg = "The report does not have a custom page. "
               msg = msg & " Do you want to define one?"
               response = MsgBox(msg, 4)
            End If
            If response = 6 Then
               'User chose Yes; change the size.
               'Initialize the Fields member.
               DM.dmFields = DM.dmFields Or DM_PAPERSIZE Or _
                  DM_PAPERLENGTH Or DM_PAPERWIDTH
               'Set the page size.
               DM.dmPaperSize = 256
               msg = "Please enter Page Length in inches"
               DM.dmPaperlength = InputBox(msg) * 254
               msg = "Please enter Page Width in inches"
               DM.dmPaperWidth = InputBox(msg) * 254
               'Update the first 68 bytes of the PrtDevMode property.
               LSet DevString = DM
               Mid$(DevModeExtra, 1, 68) = DevString.RGB
               rpt.PrtDevMode = DevModeExtra
            End If
         End If
      End Sub