Setting Up A Paid In Advance

I have a problem with figuring out how to implement what I call “Paid In Advance”. If a customer pays 4, 5, 6, or 12 months in advance, I for some reason can’t think of how to set this up with tables, queries, forms, and reports. The example that closely matches my db is “Order Entry” from access sample db’s.

Tables are as follows:
tblCustomerDetail
tblCustomerHistory
tblPayments

For every customer (tblCustomerDetail) there are multiple service records (tblCustomerHistory) and for every service record there are or can be multiple payments (tblPayments) for that one service record.

Just like in “Order Entry” where Customers have multiple Orders and then one or many Payments for that one Order. (Pretend that Order Details is in the Orders table.)

The problem that I’m having is trying to come up with a way to assign the “Paid In Advance” money to the customers account without assigning it to a service record or payment. I can’t assign it to a service record because it hasn’t been serviced yet. And I can’t assign it to a payment because the service record generates a new record in the tblPayments when a new service record is entered, and besides that wouldn’t work because the “Paid In Advance” money would only be applied to that one service record.

I hope everyone is following what I’m saying.
If anyone has any clue as to what I am trying to do, please feel free to help me.
As always any help would be greatly appreciated.

Thanks

P.S. If anyone knows where there is a sample db of what I am trying to do, I would be grateful if you could post the link in your reply.