Billing and invoicing service per member

Hello

I would like to know if there is some option on the platform for having variable prices depending on certain factors, like the quantity of users that use my service for a specific customer. This could change every month, and I would also need to apply discounts based on that quantity. Asana has something like this (https://asana.com/pricing).

Following that line, would it be possible for the platform to apply those charges on its own? (After being informed the number of users).

The flow would be something like this:

-The customer signs up with a zero base price and configurable options.

-At the end of each month, the platform asks (through a webservice in our system) the number of users the customer has.

-Based on that number and other customer configurations (discounts and such), the platform charges the customer accordingly.

Is it possible? Could you give some advice or link on how to achieve this?

Thank you.-