Sell after 3 days I bought

Please let me know how to code AFL for backtesting,
code snippet:

Buy = Low < Ref(LLV(Low, -3));
Sell = ??????
Buy = Extrem(Buy,Sell);
Sell = Extrem(Sell,Buy);

What is the "Sell" code? I want to sell 3 days after a Buy signal from above code.

Please see this for N-bar stop:

Quote from the documentation:

/* N-bar stop */
ApplyStop( stopTypeNBar, stopModeBars, 3 );