SubForm.SourceObject Property (Access)
You can use the SourceObject property to identify the form or report that is the source of the subform or subreport on a form or report. Read/write String.
Enter the name of the form or report that is the source of the subform or subreport in the control's property sheet. If you add a subform or subreport to the form or report by dragging it from the Database window, the SourceObject property is set automatically in the property sheet.
In Visual Basic, you set this property by using a string expression that is a name of a form or report.
You can't set or change the SourceObject property in the Open or Format events of a report.
If you delete the SourceObject property setting in the property sheet for a subform or subreport, the control remains on the form but is no longer bound to the source form or report.