Abstract: A computer implemented method for negotiating contracts between a plurality of participants is provided. An order is received from a first participant of the plurality of participants. Position risk of the first participant is calculated by accessing data regarding the first participant and using the data regarding the first participant in a parametric variable equation modified by control values from a simulation model, to calculate the position risk of the first member. The order is blocked, if the position risk of the first participant is in a first condition for the first participant. The order is made available for forming into a contract, if the position risk of the first participant is in a second condition for the first participant.