When the first trade is completed, the system is smart enough to cancel any other non-completed trades involving any of the players in the trade proposal. For example, Trade A contains Mike Greenwell and is accepted at 4:00 PM. Trade B also contains Mike Greenwell and is accepted at 5:30 PM. Both trades are accepted. When the trades are processed, Trade A is processed first because it was accepted prior to Trade B. As a result, Trade B is automatically cancelled because it contains a player that was involved in Trade A.