Duplicate by random and remain on stage

Hi,
I got a project containing 4 movieclips to be duplicated by random and placed on a certain position on stage.

all movieclips are placed on top of on another.
the problem is: already placed movieclips don’t remain on stage - they get replaced by the next movieclip duplicated in.

How can I make the already placed clips stay on the stage?

Please review to my attachement.

Thanx guys, you are my last resort!