Question About Negative Numbers

[Masterstitch]

hey does anyone know how you make a ability like Berserk which gives bonus attack speed and movespeed in exchange for increased damage taken to make the damage taken negative so it makes you take less damage instead of more because when you make it have a negative number it automatically swaps to 0 and i hate it i need to know how how to do it i seen it done in many other maps SOMEONE PLEASE HELP

[Arabidnun]

File -> Preferences -> Allow negative values.

Congratz!....