Reffering to dynamic movies

Hey guys,

so i am filling the stage with movies with a keypress fuunction. Each new movie is added as a new layer:

on (keyPress "u") {
	_root.collage_holder.attachMovie("anim3", "a" + (k++), k);

and i need to unload a movie that was loaded 5 keypresses before. But i am struggling with the syntax, i have tried

on (keyPress "v") {
	_root.collage_holder.attachMovie("anim2", "a" + (k++), k, {_x:500, _y:500, _xscale:30, _yscale:30});

but seemingly to no avail. Is the syntax just wrong, or is this simply the wrong approach.