How does the OrderID value get updated in the Order Details table from
within the Orders form?

If I add an order to the Order table from within its table view and
then open up the Orders form and enter data in the subform section,
this data is updated into the Order Details table along with the
OrderID from the Details table.

I cannot for the life of me figure out where this value is getting
passed from the Orders table to the Order Details table.

Thanks in advance for any clarification you can provide

Deb