create a woocomerce plugin for price

I have a wordpress site with an onlinestore using woocommerce. i have two types of products, one that i get locally and others that i import from vietnam for which i pay in usd. now the price of imported products change with the change in exchange rate of usd to aud. i would like to be able to control the exchange rate from the backend and apply to the group of imported products.
the rate i want displayed in the site = {( buying price in usd * exchnage rate ) + shipping charge } * selling margin
and i should be able to key in the exchange rate, the shipping charge and selling margin from the backend. so when i upload a product and put in the buying price in usd, it automatically calculates the retail price. Also selling margin is different for different categories, so i need a solution for that