Upgrading unit individualy

[AtivEnergy]

Greetings!
I have an unit which can build a tower building(ancient protector) and i've add an upgrade(research) on this tower.
What I want to make is that when I select 1 tower and click that upgrade only that unit upgrades(upgrade icon must dissapear for this tower). (the upgrade will give ability - spell immunity to the unit)
After i build another tower or click to another tower, i want to see the upgrade again so i can make spell immunity towers 1 by 1.
I want the upgrade to cost gold and lumber.. I don't want to change the entire unit with "upgrades to"..
It is possible?

The help will be appreciated!

 

[Uncle]

Use the Charge Gold and Lumber ability and detect when the unit casts it using this trigger:

• Events
  • Unit - A unit Starts the effect of an ability
• Conditions
  • (Ability being cast) Equal to YourAbility
• Actions
  • Unit - Add Spell Immunity to (Triggering unit)
  • Unit - Remove YourAbility from (Triggering unit)

I haven't tested it but it SHOULD work. You may need to use a different cast Event.