Aggregator program for automating actions on trading floor

The program should collect all the goods in your account, and be engaged in continuous monitoring and price changes. The program should have some simple interface where my products and prices will be displayed. There will be several sites and for each site you need to write a separate algorithm of work, and all this should be combined into one program For each product I set a lower threshold (that is, if the price of the product falls below it, the program sets the upper threshold and waits until the price rises), the upper threshold (the price that will be held if there are no competitors), and the program must constantly monitor all products and update the price.