How to replace DMS_CANCELLED

I didn't find it in the Translation. Is it somewhere else? When a user decides to cancel his order on Paypal, the following text appears:

DMS_CANCELLED
Your order is cancelled


How can I replace DMS_CANCELLED with "Order Cancelled"?

Thanks...

Hi
I added this language string to the language file. Please login to your account to download the new version and install it on your site. After that, it will work as expected .

Thanks,
Tuan