Attempt at storing a variable across proceedures. (SOLVED)

I'm trying to detect the amount of damage a player takes by setting up two procedures:

First activates before the player is damaged.

Second activates when the player is damaged.

I want to store the current health from the first one and the current health from the second one to subtract the first from the second, then if the result (the damage) is higher than 8, i want to proc a custom potion effect.