To give different exp to different hero

I don’t always hate punishing difficulties, but I think it is better to have some relaxed restriction on dungeon diffculties. I’m thinking about removing entrance restriction but make the too-high-level-heroes cannot gain exp, as it is loar friendly(in vanilla heroes say they cannot develop in easy dungeon!) But for the second part I cannot imagine where to start because of my short of knowledge on DD variables.
Currently I think I can give buffs with “resolve_xp_bonus_percent = -100%” to heroes with too high levels to acheive it. Will it be possible? Or is there any else idea where to start?