Help needed for triggered spell:

I need to make a triggered spell that does the following:

It starts when the hero begins to channel (Big Bad Vodoo), after 3 seconds it shoots a chain lightning (modified) on each enemy within range (512), after another 3 seconds it shoots a frost nova (modified) on each enemy, and after another 3 seconds it shoots a gigantic Flame strike centered on the caster of Big Bad Vodoo.

I have tried to do this, and know how you are supposed to do it, pls dont tell me to use invisible casters to cast the spells and stuff, pls tell me the exact trigger, or it wont help me. I have an invisible caster done with all the spells and that stuff. Would prefer not to use Jass, but if you can provide me with a done Jass trigger that I wont need to change, then that would be no problem.

Events
Unit casts ability
Condition
abillity being cast = to Big Bad Voodo
Action
wait(game time or real time) 3 seconds
Create 1 (invisable caster) for owner of triggering unit at location of triggering unit.
Make last created unit do Orc Farseer - Chainlighting random unit in unit group within 512 of triggering unit.

Now those 2 action must be copied and pasted about 10-20 times

wait(game or real time) 3 seconds
Pick all (invisable caster) within 512 of triggering unit and remove picked unit
Create 1 (invisable caster2) for owner of triggering unit at location of triggering unit.
Make last created unit do Undead Litch - Frostnova random unit in unit group within 512 of triggering unit.

once again do that 10-20 times

wait(game or real time) 3 seconds
Pick all (invisable caster2) within 512 of triggering unit and remove picked unit
Create 1 (invisable caster3) at location of triggering unit
Oder last created unit to Human Bloodmage - Fire strike location of triggering unit.
wait 5 seconds
pick all invisable caster3 within 512 of triggering unit and remove picked unit

I have used this method before for a laser pod spell, the attacking every unit nearby is random, so doesn't always hit everyone, but it works pretty good.