Do you want a channeling type spell with the help of Trigger ?
I told you, Wait action DOES ruin the trigger itself, therefore, please avoid it
Use a channeling-base spell OR you can just use a single-target base spell and change the Casting Time to 3.00 seconds
If you're using a channeling-base spell, every unit affected by it has a buff
Like Starfall, check every second if the caster still has the buff, if it isn't, then isntantly Turn off that trigger