Private Sub remove(La As ListBox, Lb As ListBox)
'    For i = 0 To  ? – 1
'      Lb.AddItem ?.List(i)
    Next
'    ?.Clear
End Sub
Private Sub Command1_Click()
    Call remove(List1, List2)
End Sub
Private Sub Command2_Click()
    Call remove(List2, List1)
End Sub