Listener (always listening)

How do I make an MC or other object listen always for an action to occur. I know that sounds vague and I don’t mean it to be. I’m wanting to dynamically load MCs into another base MC. The deal is the amount of child MCs is not defined. I want each MC to be “listening” for an action to occur in a base MC and in other child MCs. I tried using localConnection, but it doesn’t do the above.

Any ideas?! If I need to define in detail I can do so.