Reward Points use all points that order needs.

Hi,

I need a advice to archive this: I'm using Opencart 2.3.0.2, and i have a little problem.

I have to use all the reward points that the order needs, for example, if the order need 100, and the user have 100, it uses automatically that points to checkout the order.

My store will have the prices like 0.00€, and works only with reward points, so if the user have the reward points, it will checkout the order.

Any ideas how to make this possible?

Thanks a lot.
Regards.