I get around that by making a table of parameters. Just as the user selects the fax printer from the Printers, they just update the table with that printer name
Code would be somthing like
Private Sub Command89_Click()
dim faxprinter as string
faxprinter = DLookup("[ParameterValue]","Parameters","[ParamterName] = 'faxprintername'")
Set Application.Printer = Application.Printers.Item(faxPrinter)
docmd.openreport "reportname"
Set.Application.Printer = Nothing
End Sub