Firstly I'll repeat my earlier comment - this is an unnecessarily complicated method of working.
The correct approach is still to fix your query ... the one from the other thread
However doing this is extremely easy.
The listbox must be simple select as combos can only have one value
Both combo & listbox need to be bound to the same field - normally the primary key field which should be hidden in both controls
Add code to the after update event of the listbox:
Code:
Private Sub ListboxName_AfterUpdate()
Me.ComboName = Me.ListBoxName
End Sub
That's it!
See attached for a very simple example