Show discount price instead of discount sum

[prestalearn]

When adding quantity discount on a product prestashop shows the discount amount.

For example: When purchasing 4 or more discount is -10$

 

Does someone know how I can rewrite it to display the price if you buy 4 or more for example:

When purchasing 4 or more your price is 50$ (60-10$)

 

I run 1.5.3. THanks in advance!

Edited March 13, 2013 by prestalearn (see edit history)