Define pricing procedure for flexible price. But how?

Hi experts,

The thing I want to do: I created a new procedure which calculates order amount by the number or materials. For example if a customer buys material between 1 and 99 he or she will pay 5 euro per a material.If customer buys at least 100 material he/she pays 995+14 =499 euro total. After 99 material customer pays 4 euro per a material.But it does not work.

How can I solve this problem?

Thanks&Regards