I need to give certain products discounts every week but I cant find out how to show it in the price tag. Promotions I create in the discount/loyalty settings only show up in the checkout phase.

I cant use a different pricelist because every single customer (more than 400) has a different pricelist with different prices for each customer. 

I tried a solution of adding a formula referencing a PROMOTION pricelist to each individual pricelist. This works with the product I want to give a discount to but every other product basically turns back to default price because my PROMOTIONS pricelist has every other product in base price instead of using the other rules I have set up for each client's pricelist. 

Please help, any solution will do. How can I do a temporary set discount or a temporary price for a product that affect every customer in my database.