namespace Billing
{
    public class Customizer : MercatorUi.ICustomizers.IBillingEngineCreated, MercatorUi.ICustomizers.IBillingEngineClosed
    {
        public void BillingEngineCreated(MercatorUi.Engine.Gescom.BillingEngine billingEngine)
        {
            billingEngine.BeforeSave += BillingEngine_BeforeSave;
        }

        public void BillingEngineClosed(MercatorUi.Engine.Gescom.BillingEngine billingEngine)
        {
            billingEngine.BeforeSave -= BillingEngine_BeforeSave;
        }

        void BillingEngine_BeforeSave(object sender, MercatorUi.Engine.Gescom.BillingEngine.BeforeSaveEventArgs e)
        {
            MercatorUi.Engine.Gescom.BillingEngine billingEngine = (MercatorUi.Engine.Gescom.BillingEngine)sender;
            if (...........)
                billingEngine.ForcedBackOrders = MercatorUi.Engine.Gescom.BillingEngine.ForcedBackOrdersEnum.No;
        }
    }
}