MS Access: Populate subform data automatically (one to many relationship) in Access 2003/XP/2000/97

This is definitely possible to do. We've created a sample Access database that you can download that demonstrates how to populate a subform with data, in this case multiple records, when a master record is created in a form.
Let's take a look at the example. Below, we have a form that lists the serial number, date, and driver name.

The user will enter the new serial number (and associated data) and tab off of the Driver name field. Under the main form's After_Insert event, there is code that will run to create the 24 item number records that will be associated with the serial number (just entered).

As you can see, the 24 items now appear in the subform.