hi
sorry but this is not possible due to 99% of the time only one selection will reach half it's matched price , so you will always have 2 losing bets and the win amount on that one cannot cover the other 2 losses plus leave a profit on all other runners.
if this was possible the trigger would be worth millions due to either zero loss or profit a no lose situation , i wish that it was possible , would be nice to guarantee a profit.
mcbee