Ahh...  the age old question...  Should I use market orders or limit orders with my trading system??

If you are just starting out building your first trading system, then use MARKET orders for now.  They are easier to handle and easier for you to develop the logic behind the trading system.  Market orders generally fill COMPLETELY and fast.  So your trading system can be designed to use market orders without having to worry about "contingencies"

Limit order are, in some cases, essential to the success of a trading system.  Limit orders are a bit more complex in nature because they offer a potential for "not getting filled".  Thus, these types of orders usually require a bit more programming and trading system logic to handle.  The benefit is they give you the ability to contain "slippage" and to potentially provide an "optimal entry" for your trades.

So, in short, use MARKET orders if you are just starting to build your trading system - they are easier and require less logic.  In fact, you can even fire off market orders, then assume they fill in your first attemp at building an automated trading system.  Later on, you can add the logic to verify fills, fill prices and fill amounts.

If your system demands the use of LIMIT orders, then please review the examples in the Programming MTS section to learn how to effectively use the MTS functions with limit orders.  There are examples in this section that show how to place, poll and verify orders using MTS.