How to make a procedure that reduces specific damage to another specific value?

Im making a custom item in MCreator. It's like an armlet that blocks heavy damage.
Here's what I'm trying to do:

• There is an item called "Gilded Armlet"
• When is it weared by player, if the player takes more than 10 damage (like 50 or 11), It will be deal 10 damage to us instead.
• Then, item takes a durability damage (it has total 12 durability)

Looking for tutorial thx.