I have a customers table that is related to an invoice details table. This invoice details table has two subsequent tables related to it - Orders and Invoices. The idea is that an order can be created using the basic invoice details table, retrieving an order number from the orders table and then, if confirmed, converted to an invoice by getting an invoice number from the newly created invoice record from the invoices table. Anyway, my point is that a customer could have 5 linked invoice details records, 3 of which may be orders and two could be invoices. I want to have a calculated field that can count the number of invoices that the customer has, from the customers table. At the moment I can only count the number of invoice details records which doesnt help as I want to differentiate between the orders and invoices. The Invoice details table has fk_orders and fk_invoices fields that retrieve the serial numbers from the related tables when either is created,..