Newbie forms 3.0 question

I'm trying to develop an inventory tracking application using Oracle forms 3.0 running under VMS. I have an inventory table that looks like: table inventory (
  barcode varchar2(30),
   amount number,
   location_id number).

The barcode system uses the VMS mailbox facility for interprocess communication. I've written a user exit that gets the barcodes from the mailbox as they are scanned and returns the value to forms.

I would like the form to display rows with the information about each item removed from inventory. My question is: must I use a block without a base table to do this and perform each row query in a trigger as the barcode is retrieved and then write my own ON_UPDATE trigger to update the inventory to reflect the removal of the item or is there some way to use the base table query/update triggers built into ORACLE that I'm missing?

TIA.

-- 
Karen Silverstein                karen.silverstein_at_stjude.org
"Speaking only for myself"       St Jude Children's Research Hospital,
(901)531-2375                    332 N. Lauderdale Avenue,
                                 Memphis, TN 38101