Just a trigger

I'll need just a trigger for my spell.But I don't know what will be,so I need help.
I had the idea of creating a spell.Here's the part.
I was thinking that I summon a meteor(not inferno),where a creature appears.That's not all.
When the creature appeared,I will make it not attack and not move, 'cause other inferno meteors appear in a circle in an order.
And also,when the inferno meteors have landed in that order,then the creature can move and attack.

Well,that's classic.I want a trigger,containing this idea. Please, H-N-bert.

You don't want to use inferno for the meteors? I mean, you can use it as a base ability to get the meteor effects (with stun and damage), but not make it spawn any units.