Need a special pricing plugin for WooCommerce

Hello,

we are searching for a plugin for WooCommerce. The client want to have a normal price for the customers, and then a special price for the retailers. The difficulty is, that they want to have the price for the customers in quantity (piece), and for the retailers in weight (gram). I found already plugins, but none of them can do both in the same time, so give a special price for a specific role and also change the quantity to weight.
Somebody knows something? Thanks.