A computer based trading system implies spread markets from multiple real or implied spread markets. In particular, one aspect of the invention permits implication of a spread market from a combination of inter-commodity and inter-calendar spread orders. Furthermore, another aspect of the invention allows use of nontradeable implied or bridge markets to combine with other implied or real markets to create further tradeable implied markets. The method described herein thereby permits the creation of all implied markets that are inherent in the combination of futures, calendar spread and inter-commodity spread real orders.