Nested MovieClips

one more question. i have a movieclip and i attach another movieclip INSIDE the first one. i want the second movieclip to be equally spaced and centered in the first one. how do i do that? is it somehting 2 do with registration point??
and when i change the size of the clips, i want the size of the child to change with the parent? can anyone gimme a hint!
Thanx for ur help.
i’m very new to flash n m working on AS2.0 class architecture. so, u can say that i’m not a graphics guy.