Duplicate movieclip

i have a sqaure movieclip…

name: blockBefore
instance: BLOCKbefore
size: 20x20

my canvas is 400px wide…
im tryin to duplicate BLOCKbefore 20times along the top of my canvas…
i have the first one at 0,0 (top left corner)…
i want to know y this code dose not work…
if anybosy knows…

[AS]onClipEvent (load) {
amount = 20;
while(amount>0){
duplicateMovieClip(BLOCKbefore, “BLOCKbefore”+i,i);
_root.BLOCKbefore+i._x = _root.BLOCKbefore+(x-1)._x + 10;
i=i+1;
amount=amount-1;
}
}[/AS]
i keep getting an error here any ideas of wats wrong with this code… or of a better way to do it would be really hopeful…