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I have used the Tradestation simulator extensively and here is what I found. Normally, you should not use limit orders on the simulator, at least where there are other persons at your price on the same ask or sell. As you know, in real world non-simulated trading, if 10 persons are already at the same ask or bid amount, you will be the 11th person in line and your order will be filled only after the orders of the persons in front of you, and if the demand or supply at that price has already been exhausted by earlier bidders you will not be filled at the price you desire. The simulator, however, is set up so that regardless of where you are in line, the simulator will move you to the front of the line so that your bid or ask gets filled before everyone else's at the same price, regardless of your position in line (this information was supplied by a Tradestation techiician, although I had to talk to several Tradestation reps before I finally got an answer). The reason this occurs is that it is too difficult for the Tradestation simulator to gage the constsnt flowand changes of orders at a particular price level. Consequently, you are far better off using market orders with the simulator. This has the advantage of forcing you to exercise greater cautionin making your trades since you will usually start the trade being down because you bought or sold at the market price. Of course, if there is a gap, especially a substatial gap, between the bid and the ask, you could always try to split the gap with a limit order (place an order to buy at the current bid plus 2 cents, short at the current ask minus 2 cents, split the difference between the bid and ask, etc.). In doing so you would be best off by hiding you bid or ask so as to be be first in line for being filled at a market bid or ask without other bidders automatically adjusting their bid or ask away from you. For instance, if the current bid is 50.00 and the ask is 50.25, you could place a hidden bid at 50.10 and hope to get filled by a market order to sell. If, however, you place a bid at 50.10 that is visible to all market sellers, the sellers may think that the trend is up and might consequently immediately increase their asking price to perhaps 50.35 and not bother to make a market order since they believe that the demand for the stock is increasing. I hope this has been of some help.