Hello,
The exchange only processes standard orders, as with other exchanges. Normally in large exchanges, synchronization with the globally accepted price is done by arbitrage bots.
To have an order that moves with the market, you must create an external script that places an order, then at regular intervals it cancels the order and places another one with the new price. This is what the Exchange’s JSON-API is there for. (In the upcoming wallets6 release, the JSON-API is superseded by a newer RESTful API which is easier to use, but the existing JSON-API will still exist for compatibility with existing scripts.)
Do not simply modify the price of the limit order in the database. The reason that the order must be placed via the API, is that the plugin does checks to see if you have enough available balance.
with regards