The following code should help you:

Private Sub cmdOpenReports_Click()
 Dim varSelectedUPC As Variant
 Dim lngUPC as Long

 For Each varSelectedUPC In lstUPC.ItemsSelected
   lngUPC = lstUPC.ItemData(varSelectedUPC)
   Select Case lngUPC
     Case 1111 to 3333
       DoCmd.OpenReport "report1", acViewPreview, ,"UPC = " & lngUPC
'preview report; change to acViewormal to print immediately
     Case 4444 to 6666
         DoCmd.OpenReport "report2", acViewPreview, ,"UPC = " & lngUPC
     Case Else

         DoCmd.OpenReport "report3", acViewPreview, ,"UPC = " & lngUPC
   End Select
 Next varSelectedUPC
End Sub

This assumes that your list box is named lstUPC (multi-select, with UPC
being the bound column), that your reports have a recordset which includes
UPC (which is a number), and that you want a separate report
previewed/printed for each UPC (rather than a single report for all UPCs
within a range).  You should probably add error checking/trapping to cope
with no data, or ...   It's up to you where you take this.

BTW, a list box with over 500 items seems a little user-unfriendly ;-)

HTH,

Rob