I am building a database in Access 97. I have a company that teaches people in a class on a subject. Now before, students would come once. They register the student making sure their SSN is always different. Now students want to return. I need to make the database see endless amount of "returners". I have two tables, StudentInformation and BillingInformation. Billing has the primary key pkInvoiceNumber and numStudentID is under it as a duplication field so if StudentID 14 returns, it will go through. My problem is on the form I make StudentID 14 and then i go to another record and type StudentID 14 in the "Student ID" textbox. It gives me an error saying i need to create a many to many table. I'm not very familiar with many-to-many. Can someone please explain many-to-many or suggest a better way of looking at this problem. I need to be able to type the Student ID at anytime and see his entire history with us. Thank you in advance.

Jon