Placing a sell limit order only after a buy order has been filled


I am trying to implement the following:

place a buy limit order at $1000. place a sell limit order only once that buy limit order has been filled, so that I don’t have the ability to short (currently my backtest allows catalyst to short before the buy has been filled…i dont really know how this is possible, but w/e)

the first solution i thought of was to place the buy limit, and then immediately place a stop limit with the stop set at 1 penny above the buy limit so that the sell limit isn’t triggered to be set until the buy has been completely filled, but catalyst doesn’t support stop orders, so what am I to do?

Also, I’m noticing that catalyst is shorting despite the fact that my buy limit order is set at a lower price than the sell limit order, how is this possible?