Hi,
Very interesting lessons. However, everything works fine except:

1) When pressing the "Close All" button the "Forms in collection" returns to 0 but
   all open CustomerF" forms are still open.

2) When closing the main menu, all open CustomerF" forms are still open.

NOTE: I checked it also using the After-L4.accdb provided by you, with the sam result!

/Regards Jan Holm

I tried to solve the problem adding the following code in Form_Close of the main menu in order to close any remaing open CustomerF forms, and it worked (at least for this case).

Private Sub Form_Close()
    Dim F As Form, L As Long
    
    For L = 1 To OpenForms.Count
        Set F = OpenForms(L)
        On Error Resume Next
        DoCmd.Close acForm, F.Name
    Next L

    Set OpenForms = Nothing

End Sub