Actions to dynamically loaded movie clip

Hi.
I am making an image gallery and have so far got buttons that display a group of movie clips inside another movie clip.
onclick { _root.attachMovie (“group”,“group”,1) } or something, from the top of my head.

I now need to make it so that each movie clip inside “group” displays another movie clip, “image”. How do I do this, seeing as they are dynamically loaded?

I hope this makes sense. Thanks, Rob.