in fig1 , a general view of an example automated trading exchange system is shown . the system comprises a number of remote terminals 10 all connected to a central computer server 12 comprising a matching unit 13 including a computer processor , and an order book ( memory ) 14 associated therewith . the central computer server 12 is loaded with suitable software , such as the click tm software sold by om technology ab , sweden , and forms an automated exchange having all features and functionality of a conventional automated exchange . the remote terminals 10 are designed to send data to and receive data from the central computer server 12 . the terminals 10 are further designed to provide an interface for investors , such as broker firms etc ., trading contracts including combination contracts at the automated exchange . the matching of orders input in such a system is performed in the central computer server by the unit 13 designed for this task . in fig2 , a block diagram illustrating different parts of a central computer server 212 having an example matching unit . the example matching unit comprises two separate entities 213 and 211 . the first entity 213 is a single matching unit provided for matching all orders input to the automated exchange system . the unit also matches derived orders as generated by the system as a result of incoming combination orders . the unit 213 is associated with an order book 214 and receives and outputs information from / to remote terminals ( not shown ). the second entity 211 is a unit for pre - calculating values likely to be used by the matching unit in the matching process . the calculation unit calculates values that are close to the current market values . other more complex prediction algorithms and models may also be used taking into account price movements , volatility , etc . also more than one unit 211 may be provided . the values that are calculated by the unit 211 are stored in a global memory 215 . the memory 215 is accessible both by the matching unit 213 and by the calculation unit 211 . the provision of the global memory comprising values to be used in matching process enables the matching unit to execute the matching fast , since if a value requiring complex calculations is required this value can be fetched directly from the global memory 215 . hence , the matching unit does not need to use any of its own processing power for performing these calculations . thus , the matching process of the matching unit can quickly and easily use the values calculated by the calculation unit . if a value is needed in the matching process and it the value does not exist in the global memory 215 , the calculation unit is called upon to generate that value in real time . in a preferred example embodiment , the process within the calculation unit also calculates new values that are likely to be required by the matching unit when this first query is answered in order to minimize the number of queries . this because a query slows down the performance of the matching compared when the value can be found directly in the global memory . the number of values that can be pre - calculated may or may not be configurable . if many values are calculated in advance , the performance will be high , since no or very few additional calculations will be required and passed on as a query to the calculation unit . however , many pre - calculated values will require a large memory . if less pre - calculated values are used the performance will worsen if the volatility in the market is high but the memory usage will be low . therefore , a trade off between the cost for the memory and the performance level will have to be made . also , the use of a prediction model tuned for the financial instruments traded at the automated exchange can be used to minimize the number of queries . also , as stated above , the number of units ( partitions ) provided for pre - calculations of values may be more than one in order to even further speed up the execution . in fig3 , a flowchart illustrating example steps carried out in the matching unit as described above in conjunction with fig2 is shown . the matching unit matches incoming orders as well as derived baits . thus , first , in a step 301 , a combination order is received by the matching unit 213 . the unit then tries to match the order with a corresponding combination order at the same price and volume , step 303 . if the incoming order cannot be matched with another combination order the incoming order the matching unit tries to match the combination order with single orders in the outright market . for the incoming combination order to be matched with outright orders the outright prices and / or the volumes for the combination order must to be calculated . if the corresponding price and / or volume is given such that their values easily can be calculated the matching unit 213 may calculated them , step 305 . if , on the other hand , the corresponding price and / or volume is given by a formula or is for some other reason determined to place a too high load on the processor associated with the matching unit , the matching unit 213 fetches the values needed for the price and / or volume calculation from the global memory 215 , step 307 . using the values calculated / fetched in steps 305 and / or 307 the matching unit 213 tries to match the separate legs of the combination order with corresponding orders in the outright market , step 309 . if the incoming combination order cannot be matched in either step 303 or 309 , the order is placed in the order book of the automated exchange , step 311 . when placed in the order book the matching unit 213 will try to create baits / derived orders from the outright order in the legs in the combination , step 313 . the values used by the matching unit 213 may vary depending on what instruments are to be traded . for example , when bonds are to be traded price - to - yield calculations are done by the calculation unit 211 for fast access by the matching unit 213 to calculate the prices of the outright legs . the matching unit also needs the duration of the legs for the calculation of the volumes of the legs . thus , in this example , both the price - to - yield , yield - to - price and duration calculations will be done in the calculation unit 213 . all these calculations are very computer intensive and thus can not be performed by the matching unit 211 without rendering a bad performance for the automated exchange . in the example of a covered option trade the matching unit 213 needs the delta values of the outright legs to calculate the volumes but no calculations need to be done for the price determination . thus the values needed by the calculation unit 213 may differ depending on the instruments traded . when there are combination orders placed in the order book and derived orders are calculated and placed in the order book , the matching procedure has to be run again whenever a price in the outright instruments are changed or a new order is entered in the outright market , step 315 . the procedure will be similar to the one described above in steps 301 - 313 , when an incoming combination is executed . in either case if a new order is entered far away from the last or the market price existing in the market the values requested by matching unit 213 from the memory 215 may not exist in the memory 215 . this is described below with reference to fig4 . in such a case , first the unit 213 tries to access a value in the memory 215 , step 401 . if the access fails the unit 213 sends a query to the calculation unit 211 requesting new values , step 403 . the calculation unit 211 will then interrupt its current calculations and calculate the value ( s ) requested by the unit 213 , step 405 . next the calculation unit 211 will add and remove values from the global memory 215 , step 407 . the new values will be based on the current market prices . in this manner , the probability that the matching unit 213 again has to query the calculation unit 211 will be reduced . when the memory is updated the calculation unit 211 notifies the unit 213 which now can read the values from the memory 215 , step 409 . in another preferred embodiment the requested value is first calculated and returned to the matching unit before the memory is updated . the calculation unit may preferably continuously receive market data so that it can pre - calculate the most likely values to be used by the matching unit 213 . the calculated values may , for example , be all the values a standard deviation ( volatility ) away from the current market values . the matching unit 213 will use the values received from the global memory 215 or the calculation unit 211 to calculate the price and / or volume for the baits . thus , the matching unit will be likely to do some calculations , but the process intensive calculations as iterative goal seeking , price - to - yield conversion , black and scholes option pricing formula etc . are performed by the calculation unit 211 . the example methods and systems described above make it possible to create combinations where the volume and / or the price is / are determined according to a formula instead of being fixed ratios as most electronic trading systems are designed to handle today . the systems and methods can also guarantee that all parts of the combination will be executed since the execution is done in the matching process .