As: Help with random movvement

I’m tryng to attach dynamicaly several instances of a movieclip in the library. And i want them to be placed in random position on the stage. After a few moment they would disappear and would be replaced by new instances of teh same movieclip (these new instances should also be placed in a random position).

here is the pseudo-code

Attach movieclip instances to stage in random positions
Count time;
Remove the instances ( not in the same time, but one by one)
Attach new instances and so on
Can anybody help me with coding?