% return on an individual trade:
outlayed capital = # contracts * margin
gain or loss = (point value * # contracts * + or - point change ) -(slippage + commission)
% return = (+- loss or gain ) / outlayed capital *100
Its probably better to put your return in terms of your total capital, and your individual returns in terms of dollars risked for information purposes
instead of outlayed capital, use dollars risked = % of total capital risked / (pointvalue * volatility)
% return = (+-gain or loss) / dollars risked *100