Array menu with subs expand and collapse

Hi,

I managed to make a array menu very simpel. But i’m trying to figure out how i can add sub items to main items. And how to expand and collapse on action.

So basicilly i have 2 main items Lets say Intro and Outro.
When a user selects intro i want it to expand and view 2 new items (the subs), outro has then moves to the bottem making room for the subs (the animation works horizontal). And if Outro has been selected the already expanded subs collapse, outro moves back to his old position making room for his subs to expande beneath him.

Schematics:

Intro
Outro

Intro
----Hello
----Come Again
Outro

Intro
Outro
----Bye Bye
----Talk again

So all of this is working with Arrays and some actions.
I have been searching to the forums but i cant seem to find the light!!!

Anyone please suggestion, tips, links.

Great much thanks