Solved How to do this

[zide]

How to do this:
When a player right click a wooden stick,make him shot a snowball that can cause 10 damage?
Sorry for my bad english.
My minecraft version is 1.12.2.

 

[MartinOdum]

on right click holding stick:
    make player shoot snowball with speed 1
    set metadata value "SpecialSnowball" of shot projectile to true
on damage:
   if victim is a player:
       if "%damage cause%" is "projectile":
           if metadata value "SpecialSnowball" of event-projectile is true:
               set damage to 10

Requires skellett for the metadata part

Edit: Also the damage would only work on other players, you can change that by removing the if victim is player condition

 

[zide]

on right click holding stick:
    make player shoot snowball with speed 1
    set metadata value "SpecialSnowball" of shot projectile to true
on damage:
   if victim is a player:
       if "%damage cause%" is "projectile":
           if metadata value "SpecialSnowball" of event-projectile is true:
               set damage to 10

Requires skellett for the metadata part

Edit: Also the damage would only work on other players, you can change that by removing the if victim is player condition

Thank you very much!!!!!!!!!!!
And if

if damage cause is projectile:

don't work in my computer,
will

if "%damage cause%" is "projectile":

work?