Setting the carriers

[shutzu]

I want to setup TNT as my carrier. the problem is that after 9 kg for example, they charce 5.4 eur for every kg. How do I do that in prestashop without adding weight rangeses like 10-10.999, 11-11.999, 12-12.999 .... all until 300 or even 500 and then calculate the price. (p.s. I already done this, using phpmyadmin and csv download/upload. the problem is I dfon't like how it looks.)

There must be something like if weight higher than 10 kg, add 5.4 eur for each extra kg

My client is selling iron made stuff so.. kinda heavy