Making a trigger spell with a target

I dunno if this has been posted somewhere else but if you want to make a trigger spell with a target I have come up with an easy solution here.

When a ward is dropped, it is 'summoned' which triggers the well known event: A unit owned by player X is summoned

So it doesn't replace any original ward, you have to check the unit-type of the summoner too.

Look at this:
Events
A unit owned by player 1..12 is summoned
Conditions
(Unit-Type of Summoned unit)) Equal to Healing Ward
(Unit-Type of Summoning unit)) Equal to MyHero
Actions
...Your spell... Use Position of (Summoned unit) to find the location of the spell.
Unit - Remove (Summoned unit) from the game

I suggest you make a new custom spell based on either Healing Ward or Sentry Ward. Healing Ward if it's an area of effect spell (so the circle appears, set the AoE of the spell to the same as the actual spell).
Sentry Ward if it's just a point.

If the unit can already make a Healing Ward, use Statis Trap instead. If it uses both.. tough luck.
If it uses Sentry Ward already then... tough luck too.

So if you were planning on giving the witch docter a 4th ward then you're going to find another way.

The conclusion is that there are only 2 downsides of this is:
You can only make pure trigger spells with this. No mix of Ability and trigger.
Units already using wards might not be able use this (see above).

Again, I don't know if this is common knowlegde or has already been posted.

you could also use serpent ward (for non-AOE spells) in TFT