1. A method for facilitating trading of securities over a computer system, comprising the computer implemented steps of: electronically receiving a first buy or sell order for a security from a first user; calculating a block price range for said security, said block price range having an upper end and a lower end; determining that said first order has a price that is reasonably priced, wherein said price is considered reasonably priced if said price comprises either: for a sell order, said price is equal to or lower than said upper end of said block price range, or for a buy order, said price is equal to or higher than said lower end of said block price range; transmitting to a second user an electronic notification that a reasonably priced order for said security is present, but without notifying said second user of the side of said first order; receiving a second order from said second user, wherein said second order is a contra to said first order and said second order nearly matches but does not cross said first order; transmitting an electronic contra order notification to said first user after said second order is received, said contra order notification indicating that a nearly matching contra order is active within the system; transmitting a second electronic contra order notification to said second user after said second order is received, said second contra order notification indicating that a nearly matching order contra to said second order is active within the system; receiving a third order from said first user, said third order being a contra to said second order and crossing said second order; and executing a trade comprising said second order and said third order.