how can I make an attribute affect frenzy check modifier?

I'm 100% sure it is possible, because we have done it in the past. but the solution was left on the previous site and I can't remember how to do it again...

it was something like if;

CHA > 0 , add +1 modifier
CHA > 1 , add +1 modifier again

I just can't recall how to type it in terms of traiteffects.txt