Need help with spell activation overlay

[VeenixO]

Hi all, new here!

First time trying to make an addon and wanted to make something that in my mind seems simple.
Seems that it's not as simple as I thought.

Basically I want to make an addon that shows a texture when Hammer of Wrath procs or is useable (like when Blade of Justice procs). This is the code I have atm but it doesn't seem to work.

local f = CreateFrame("Frame")
local spellID = 24275 --Hammer of Wrath

f:RegisterEvent("SPELL_ACTIVATION_OVERLAY_SHOW")
f:RegisterEvent("SPELL_ACTIVATION_OVERLAY_HIDE")

f:SetScript("OnEvent", function(self,event, spellID, ...)
if event == "SPELL_ACTIVATION_OVERLAY_SHOW" then
if (arg1 == "24275") then
print("Hello, WoW!")
end
end

if event == "SPELL_ACTIVATION_OVERLAY_HIDE" then
if (arg1 == "24275") then
print("Bye")
end
end

end)

Could anyone give me some advice on how to check when Hammer of Wrath procs/is useable?

Thanks alot in advance!