Display expiration on specific protected post

Hi guys,
I just bought the pro version and I want to display on posts I’ve protected a number/countdown/time/date (whatever)… well something that tells the users for how long he will have access to the specific post/page item he purchased. I don’t want to create Custom Post Type to insert PHP code, I’d rather use a short code. As said before, anything that gives a clue on page expiration time for the current user will be fine for me.