I have the following set up. I have a [Master File]![Project Name]. Each project then has multiple openings that include a door and a frame as well as frame and door options. I have a form that will group together multiple records as a set of items for an opening as a subform of the Opening form. I then can assign door numbers for openings that use the opening items. I need an automatic way of keeping the opening items together as a set of records for an opening. Right now, I have the [Opening]![Opening ID] set up as an auto number. I then have the [Opening Items] form as a subform of [Opening]. I want the [Opening]![Opening ID] value assigned as soon as I create a record (for example, enter a value in the [Opening]![Opening Items]![Qty] field.

Any ideas how I can do this?