Duplicating MCs help

Hi all,
I’m trying to make a version of this:

http://education.smarttech.com/NR/rdonlyres/B71ECA1B-BAD0-4B17-9733-280E71D5E41D/0/fractionWallAU.gif

in flash. The basic idea is the user builds a wall of blocks which are made up of 1/2, 1/4 and 1/8 blocks- buttons inside movie clips. They then build the wall to make 1 (or a whole) on each row.

I’ve got them duplicating once, when I press a button, but when I press it again, the last duplicated clip (of either of the 3 blocks) disappears and the one I asked to duplicate appears as it should. I’ve got a :

[COLOR=royalblue]i = i +1;[/COLOR]
[COLOR=royalblue]then duplicateMovieClip code so the depth should be going up.[/COLOR]

Hmm… any help would be greatly appreciated because it’s doing my head in now.

Thanks :h: