Shipping Costs Via Percentage

[Noodleman]

Hi,

Is it currently possible to set variable percentages for postage costs depending on the total cost of the order?

For example, at the moment my post system works out values as follows:

Orders UP TO and including 6.98 = 29% of cost P&P

Orders UP TO and including 20 = 24% of cost P&P

Orders UP TO and including 57.98 = 18% of cost P&P

etc.

Is it possible to do a similar thing? or is it a flat rate percentage for all items?

Thanks :)