Projectile defense

I want to make an item that while I'm holding it makes every project that tries to hit me
unable to do so, as he will return with double the damage.

I think this can be done as follows:

A) If: player has item "Tal" by pressing the left button
B) Do: Check if a ready project
C) If you have: Check his damage
D) Multiply his damage by 2
E) Check project direction
F) Unspawn the original project
G) Respawn the projectile with double damage and in the opposite direction.

But I don't know which blocks to use from step "B"

Does anyone know what blocks I can use?

Sorry if my English isn't very good, I'm using Google translate.