undoing changes in database

First of all, sorry for any mistakes in my english. I will try to explain my problem to get an idea of how to solve the problem. My problem is that I have an application wich for every item of a sale it have to decrease the stock, but sometimes I discovered that the user to hold the item for one of his clients closes the application to sell it later (there are 35 users making sales at the same time), since I save these items on a table , at the end of the day I can see if there are some items to be returned to stock.What I want to know is that there is a way to return these items to stock at the moment in wich the user by any reason closes the application.
Thanks for your atention.

P.S - I use oracle 9 with delphi 7