If you have the historical minute level OHLC bars, you can aggregate them into pseudo-daysession bars (starting at 10:30 and ending at 15:45). Then you only need one pass through the pseudo-bars. A "coin-flip" simulation is unnecessary as it would, given enough "flips," converge on a daily basis to:if you want to play with minute level OHLC data, specifically toward this study
if both H minus O and O minus L are larger than 0.5*ATR, then you lose ATR on the day;
if neither is larger, no trade and you lose/make 0;
if one of H-O or O-L is larger than 0.5*ATR then your P/L on the day is: C - O - 0.5*ATR.
Sum the daily P/L and divide by 2.