Just in case anyone needs to do this here is an example:
1. Create a different footer for your support and cart area (eg. footer_support.tpl and footer_cart.tpl)
2. Move all your footer code into the new files
3. Add this code to your default footer.tpl
Code:
{if $SCRIPT_NAME eq '/whmcs/cart.php'}
{include file="default/footer_cart.tpl"}
{else}
{include file="default/footer_support.tpl"}
{/if}
Matt thanks for pointing out $SCRIPT_NAME .. I wasn't aware that variable was available in the templates.