I am designing a market experiment where participants serve as sellers, and buyers are simulated by the server. 

Sellers can post prices for their items, and buyers (each only needs one item) arrive at random time intervals to check whether the best price is lower than their willingness to pay -- if it is, a transaction occurs, and the seller's item and the buyer are removed from the market. 

Can I implement this using a timer on the server side? After checking oTree documentation, I am not sure whether this is possible.