[TR] football green up with more potential win on one outcome

https://community.welldonesoft.com/marketfeeder-triggered-betting/green-up-football-after-a-goal-with-option-to-adjust-stakes-on-each-outcome/

just after a simple trigger really

if i lay the draw for lay amount "la" at 2/(lay_price-1)  then i have say potential win of 100 if i lay it at 1.5 for 50 liability

now if i want to back the draw if the game goes level, i want to back it at back amount "ba" using half of my potential winnings (half of the 100 on the draw)

i tried using la/2 as the "ba" but there was an error so the logic isn't right

so i'm just after a trigger that does something like that 

cheers