How would I make a mapwide hex spell?

How would I make a mapwide hex spell?

I'm still a noob to making spells and triggers and I'd like to know what I'd have to do for a mapwide hex. (The spell must be a slam)

A slam? What is a slam?

For mapwide hex:

Event: A unit begins casting ability
Condition: Ability being cast equal to <dummy spell with no target>
Action: Unit Group> Add every unit in <playable map area> matching <owner of <picked unit> equal to enemy of owner of <triggering unit>> and do actions:
-Unit> Create 1 <dummy unit with hex spell> at <position of picked unit> facing <picked unit>
-Unit Group - Pick every unit in (Last created unit group) and do (Unit - Order (Picked Unit) to Orc Shadow Hunter - Hex (Random unit from (Units owned by (Owner of (Targeted unit)) matching (((Triggering unit) belongs to an enemy of (Owner of (Last created unit))) Equal to True))))
-Unit Group - Pick every unit in (Last created unit group) and do (Unit - Add a 0.50 second Generic expiration timer to (Picked unit))

Slam is a neutral hostile spell like Thunder Clap.
Then, I think you need to pick every units within X range of casting unit matching belongs to an enemy, store these units in a Unit Group variable and use the for each integer A, create a dummy and order last created unit to cast hex....!
If u don't know how to do, I can explain step by step to you.

Using Last Created Unit doesn't always work, as I've discovered, you have to use Last Created Unit Group for maximum efficiency.

Huh? Ok, I don't see the point of all the actions. Here is my idea: You create a dummy for EACH enemy unit, you give hex to the dummy, add expiration timer (so that it dies over time) and then order it to cast hex on the current unit.

Event - An Unit Starts the effect of an Ability
Conditions - (Ability Being Cast) equal to <dummy spell with no target>
Actions - Unit Group - Pick Up Every Unit Within Playable Map Matching Condition (((Matching Unit) is an enemy of (Owner of (Triggering Unit))) equal to true) and do actions
-> Create 1 <dummy unit> at (Position of (Picked Unit) Facing 0.00
-> Add <hex spell for dummy unit> to (Last created Unit)
-> Unit - Add a 0.50 seconds Generic Expiration Timer to (Last Created Unit)
-> Order (Last Created Unit) to Orc - Shadow Hunter - Hex (Picked Unit)

That is all!

~Daelin