...this isn't necessarily one-to-many, could be many-to-many..as it is a typical line-item table, ie it's a composite primary key made up of 2 foreign keys. If this database uses or will use any other tables besides this one, then I'd recommend to switch to using a database system now. This will simplify and standardize all your data handling (through SQL,) and keeps the database consistant according to relational rules...so you don't end up with widowed records etc.
Chris