We claim: 1. A system for processing trades of securitized instruments based on security orders and quotes received from client computers, comprising: at least one server computer comprising a memory, and a processor, said server computer configured to perform the steps of: receiving orders and quotes, wherein specified ones of said quotes belong to a quote group, and wherein said specified ones of said quotes have associated trading parameters comprising a risk threshold; generating a trade by matching said received orders and quotes to previously received orders and quotes; storing each of said orders and quotes when a trade is not generated; determining whether a quote having associated trading parameters has been filled as a result of the generated trade, and if so, determining a risk level and an aggregate risk level associated with said trade; comparing said aggregate risk level with said risk threshold; and, automatically modifying at least one of the remaining said specified ones of said quotes in the quote group if said threshold is exceeded.