one time charge question for my app

[massiv]

I need to know if this use case is possible with Shopify. I have a business that generates product videos, and I would like to create an app where users who install it can select the products they want videos for. After selecting the products, they would be charged for those videos. I was thinking of using the Shopify Billing API, but I’m not sure if this is possible. Does anyone know if this type of app can be done?

The idea is basically to charge a set amount per product selected, and the customer can return to the app and order more product videos as many times as they want.

Or is the one-time charge only for customers to access the app with a single payment and never again?