Multiple Carts & Customer Centers--PLEASE HELP!!!

I just added the multisite module for an additional webstore that mirrors the design of the first webstore but with a separate shopping cart and customer center. Thanks to previous posts, I learned how to add a new custom customer center via managing roles/users. I have the new customer center set-up but am having difficulty figuring out how (and where) to point each site to the correct cart/checkout and the right customer center. The current link to the checkout for both sites is:

<div id="headerright">
<div id="headerlinks"><NLUSERINFO> | <a href="<NLCHECKOUTURL>">Checkout</a> | <img src="/site/images/misc/cart_icon.gif" alt="Shopping Cart" /> <b>Shopping cart:</b> <NLCARTITEMCOUNT> items</div>