Button to set markup, make plug-in

We have integration with one of the suppliers, the code is proprietary. By default in the code is set a markup of 10%, manual price improvement is possible. Simply, when the supplier activates the product for us, it is added to the purchase price of 10%.

It is necessary:

- make a window / plugin for these products with so that we can automatically set a markup of, for example, 10%, tomorrow change to 20%, etc.

- changing the markup value should update all prices automatically

- set price rounding up or down

The code is generally written for this function. It just needs to be "extracted" so we can control it.

I ask for bids only from people who have a good grasp of programming, automation and the CRON function. I don't want a situation where through wrong code the site and products will crash. It is necessary to approach this with a head.

Both stores are set up on Woocommerce. Please provide me with a quote or contact me in advance, I will provide access to the code so that a reliable quote can be provided.