Magento Amasty Coupons with One page Checkout

[mjmaster]

In my site, i use amasty multiple coupons with one page checkout ( onepagecheckout.com ). Multiple coupons are work fine with default magento checkout, but with onepagecheckout, it accept only once at a time(with ajax enabled and disabled), Is there any solution to fix this(accept multiple coupons at a time)? Need any changes in this folder files:app\design\frontend\base\default\template\onestepcheckoutapp\design\frontend\default\default\template\amcoupon\checkout\cart\coupon.phtml