Upgrading a skill by triggers

I want to know how to upgrade a custom hero spell (based off of a unit spell) by triggers. I tried the learn skill thing and type in the Spell ID but it doesn't upgrade it.
Or if anyone has a way to make armor reduced on a enemy unit without using a skill, that would be great too.

Leveling a spell with triggers & upgrade is quite easy:
1. You create a custom upgrade with effect "Ability Level Bonus", and make sure the ability effected is the one you want.
2. You make the upgrade available for your unit by adding the upgrade in the field "Techtree - Upgrades Used" of your unit (often this is the point, which gets forgotten...)
3. Now you can add the spell with the trigger action "Unit - Add Ability" and you can make it a higher level with "Player - Set Current Research Level" to the desired value.
You can use any events you want (button clicked, chat message, whatever)

I'll try that. Thanks.

doesn't work. I made the upgrade. i had 1 level on the ability be defualt and then i made it so that the upgrade went up when i do a action but when ever i use the trigger to make the unit cast the spell it stays at level 1.