Item in hand that was used to attack

I made an enchantment that gives an effect with a random chance when you hit a mob. 
The issue is that I use BetterCombat mod so i can use 2 weapons. So how can I make a condition that would check item-that-was-used-to-attack instead of item in main hand or in off-hand.

This is my current "build" which sucks cause even if I hit a mob with off-hand weapon that has no enchantment I would still get the effect if my main hand weapon has the enchantment.

https://ibb.co/bbDnkq7