Tables :: Delimitate Possible Values For A Field

I got one database, consisting basically in two tables, one for "customers" (basic data, name, place and date of birth and so on) and other for "customers' orders". To avoid duplicated customers' "cards" i put on first table name's field indexed value yes (no duplicates).The problem is in the "customers' orders" table. I need to avoid anyone using the database inserting new "customers' orders" if the customer is not yet in the "customers" table (obvious) or by misspelling customer's name, to lose that order (the primary function of the database is to access to the list of all orders of a specific customer).

I thought in create a validation rule that deny any value in name field of "customers' orders" table if it is not already inserted in name field of "customers" table, but seems that validation rules doesnt work between tables, is that right?I also thought in create a query with names of "customers" table, and use it as row source in name field of "customers orders", and giving value yes to Limit to List property. This one seems to work, but i'm only testing it with few values, the database will grow to thousands of customers and i'm afraid that that rig will not work then. Also, is a bit annoying that with this solution, autocomplete is always present.