Information regarding the current state in the market is used to prevent orders from crossing. In an example provided herein, when an order is entered into a market, information regarding current positions in the market is taken into account to determine whether the order will cross with other orders. If the orders would cross, appropriate action is taken to prevent the crossing of orders in a way suitable for the person or persons trading. The teachings described herein may be used for any reason to prevent orders from crossing. Moreover, they may be used in other areas of trading to assist the trader in obeying any other rule or regulation that might involve analyzing current positions in the market before taking action.