{author_sort}. How to get the author's last name in capital letters?

Hello,

When I am using "saving ebooks to disc", there is a template that I can use to create the file name of that ebook that it is going to be save.

Today, I am wondering about the {author_sort}.

If the name of the author is "Aldous Huxley", and I use the code {author_sort}, the name in the file will be like:
Huxley, Aldous

But what I want is to get this:
HUXLEY, Aldous

In other words, just to have the last name in capital letters and the first name normal. How can I do that??

Thanks!