OSC mod porting - more help please - another code problem

I'm trying to insert this segment of code from osc's shopping_cart.php file. Having compared the code, i have found it needs to be placed in the tpl_shopping_cart.php file. All of the code except the line below is working.

Code:
$freebie[$p]['message'] .= sprintf(TEXT_QUALIFIED_FOR_GIFT, $currencies->display_price($gift->['threshold'],zen_get_tax_rate($gift['products_tax_class_id'])));

Can anyone give any advice on this? I took the assumtion that ['message'] was related to the $messageStack function of zen, but i have failed in all my attempts at modifying the code so far.

Any help gratefully received

Thanks
Steve