w3 total cache cdn background url rewrite problem

firstly sorry my english. i hope understand me.

i am using w3 total cache and aws for cdn. its working good. but i have a little problem for background urls. <div class="slide-box" style="background:url(<?php wp_get_attachment_url( get_post_thumbnail_id( $post->ID ) ); ?>) no-repeat;">

<div class="slide-box" style="background:url(http://www.212medya.com/wp-content/uploads/2011/04/yeni-nesil-web-tasarim.jpg) no-repeat;">

i want to change like this<div class="slide-box" style="background:url(http://cdn.212medya.com/wp-content/uploads/2011/04/yeni-nesil-web-tasarim.jpg) no-repeat;">

background url dosnt rewrite to cdn. how can i fix it