How can I make a Mace-like item

So im not the best in mcreator. Im trying to create a Hammer item that Deals extra damage, depending on your falling hight, tried it by making two variables one changes depending on the y coordinate depending on when the Player last were on ground and the other when the entity gets hit and finally the First variable minus the second gives the extra damage, but it doesnt work like I want it, the player gets constant damage and I don’t get any extra damage can someone help me? Thank you in advance