How to edit vendor contract costs on Sage 300 Purchase Orders Steps: Open Purchase Orders > P/O Setup > Vendor Contract Costs.Choose to edit costs by vendor number or item number.Enter or select the number of the vendor or item that you want to edit.Double-click the line containing the costs that you want to edit.Press F1 again for help on editing item cost details when the Vendor Contract Costs screen appears.Click Save. Sage 300 Request Support