Cost Price While Purchasing

Hi!

I have been using Aronium for quite a while, and it's great software. However, i have a very big and concerning issue. I am a wholesale worker, os i have a lot of products, more than a thousand, and the cost prices of them change every month. 

However, they don't automatically appear in the Purchase. When i create a purchase document, the price is 0, or the one used for the previous purchase. What should i do in order to update all the cost prices automatically? like importing an excel file, just as we do for sales?