[Trigger] How do i make item spell upgrade?

[Shanghai]

Does anyone know how to make simple spell uppgrade like change the spell to another one better?

First i need very detailed help because im not good into triggers.

What i need is following.

When i buy item (upgrade spell)

then my ability gona change to another ability thats do more damage.

How do i change ability when buy an item? anyone?

 

[GreeN!X]

Have different items with the different abilities and change them through triggers.

EDIT:
Too lazy to post the triggers. Here's the map instead.

 

[Shanghai]

+ rep thnx

But it wont give new ability..

i mean like the hero have an ability/spell called impale 1.

then if i buy an item in shop called for example impale uppgrade.

Then i get a totaly new spell. Like impale 2.

 

[GreeN!X]

So when the hero acquires the item, he gets an ability. So, meaning the item does not have any ability but it gives the hero an ability?

 

[UndeadImmortal]

Here, no trigger needed, + stores cooldown.

 

[Shanghai]

nice thnx + rep