Swap Depth of pageflip components

I want to swap the depth of two overlapping ‘premium pageflip’ components on one layer of an mc.(when you roll over one, it has to come to the foreground)
my problem is how to adress the mc’s.
so far I’ve got this as actionscript :

onClipEvent (enterFrame) {
myBook.onrollOver = function() {
_root.x +=2;
_root.myBook.swapDepths(_root.x);
}
}

but obviously that’s not working…