[Dongan]

just a note. I have tried the above code. couldn't figure out why it is not working. but this simple code works.

Found

{assign var="button_href" value=$button_href|cat:" if(checkRequired()) document.checkout_form.submit();"}

and replace

{assign var="button_href" value=$button_href|cat:" if(checkRequired()) this.disabled=true; document.checkout_form.submit();"}