What does what happens after your order is filled have to do with your limit order execution price?
If you want protection from price decreases after a buy, also put in a stop order (which will turn into a market order) or a stop limit order (which ensures execution at the specified limit price) but which may not execute if the price movement is highly volatile.
If you want protection from price decreases after a buy, also put in a stop order (which will turn into a market order) or a stop limit order (which ensures execution at the specified limit price) but which may not execute if the price movement is highly volatile.