It will work because you'd be hosting the script somewhere else, not SBI!. But of course that involves buying another domain and hosting so keep that in mind. So what you'd do is install the script code on the 2nd domain/hosting account and when the code calls for the script files you'd have to change the path to
http://www.otherdomain.com/scripts/script.php (or whatever the name of the script is).
It may end up being more work than you want to do but it also greatly depends on how complex the card script is. That is the bigger issue because every script is going to be different and call for different things. If the card script is complicated then it may just be best to create the entire ecard function on that new domain, make the design look like your SBI! site and then just link over to that domain from your SBI! site.