Auto-special tiers on specific time

Hello to all,

I currently run OC 1.5.4.

I'm searching a way to auto-special latest products.

I'll explain in more details, concept is this:
I put products on website and automatically I'd like the system to recognize it as auto-special product with a fixed % discount. I want that special automatically end in 24hrs or 48hrs from when I put on site.

That's because usually I do not create manually the product, but I import them from an external manager.

Even better, if there's the possibility to automatically scale the % discount
Example
until 24 hrs 30%
until 48 hrs 20%
until 72 hrs 10%
and so on

Do you know if there's some extension which can do this?
All I found was based on category so it is not the case.

Thank you very much