If your users log on to your application with their name/ID saved in a table you can save this log-in name to another table with details of what they are locking and then use this to inform other users trying to access the locked item. To try and make sense of that... for example I log users on with an ID ,say 'MIKE', When MIKE opens an order that I want to lock I save the order number and user to another table. When another user fails to open the order because it is locked it checks the table and sees that MIKE is using it and puts up a nice message telling them to call MIKE to free up the order...