Pool of Funds

Need help determining what Oracle's capabilities for a "Pool of Funds" is:

The use case - the customer is making an advanced payment resulting in an on account balance. As invoices are generated for services, we need a mechanism to selectively apply specific invoices against these on-account balances. Hoping to find a consistent and streamlined way of solving for this.

This prepayment is considered a "pool of funds", and the customer should be able to view the pool balance, as well as the consumption against the pool to date.

Has anyone encountered this requirement before? If so - how do other Oracle customers manage similar challenges?