Attaching multiple MC's into An existing MC

Hi > I am dynamically placing a bunch of MC’s into one MC via a loop from the Library.

It isn’t working, and I cant understand why not. If I just put them on the _root, the code works. But when I attach them inside the MC ‘banner’ - Only the last attachment attaches. :frowning:
It’s something to do with it’s depth then?! But I have a getNextHighestDepth() firing.

Can you see where I have gone wrong?

blocks = 20; //no. of blocks in row
bwidth = 31; //block width
row = 2; // no. of rows
for(r=0;r<row;r++){
    
    for(i=0;i<blocks;i++){        
 
banner.attachMovie("block","row"+r+"block"+i,this.getNextHighestDepth(),{_x:(i*bwidth),_y:(r*bwidth)});
    }
}

Ideas?