Refering to one level down

How do you refer to the level one below the current level . I know _root refers to the bottom level, parent refers to one level above but I don’t know what to use for one level below. Otherwise, is there a way to refer to a level by its name?

For my needs, I have a clip portfolio.swf that is loaded into a Base flash file. Within portfolio, is a loaded movie called Gallery.swf.
Gallery contains a movieclip called Thumbnails which has buttons to load various image.swf files. Also within Gallery is an empty movieclip called “ContainerMC” which is where image.swf are loaded into when called upon by the thumbnail buttons.
From within Thumbnails, I want to be able to refer to that movieclip “ContainerMC” which those selected image.swf files are loaded into. I can’t use _root as that will refer to the base flash file. I can’t use “this” as that refers to the Gallery file.

I’m stumped.