Quantity in Price Break window is not auto-populated when a new line was added

When user entered a new line in a contract, the corresponding data will be populated in Price Break window. Before R12, 0 will also be automatically populated in price break window but after R12, the 0 quantity would not be populated. If a user wants to add a new break price in the price breaks window, 0 quantity would not be automatically populated either (before R12, it would be populated). I tried to do a form personalization to make 0 quantity automatically populated but could not find the proper Trigger Object for the Quantity in Price Breaks window. Can I