[AccessD] OpenArgs question

This should be an easy one. The following event procedure opens a report and
passes the list box' value as th OpenArgs setting.

Private Sub lstCategories_DblClick(Cancel As Integer)
  Dim str As String
  str = Chr(34) & Me.lstCategories.Value & Chr(34)
  Debug.Print str
  DoCmd.OpenReport ReportName:="Catalog", _
      View:=acViewPreview, _
      OpenArgs:=str
End Sub

Problem is, I can't get the report to recognize it -- in any report event.

Reports!reportname.OpenArgs
Me.OpenArgs
rpt.OpenArgs

I've tried all three in most of the report's events after opening it via the
form and the setting isn't making it to the form. Any clue what I'm doing
wrong?

Susan H.