请教各位：中怎样把listbox1中选中的内容增加到listbox2中

Dim i, j As Integer
        Dim zjbd As Boolean
        zjbd = False
        If ListBox1.SelectedIndex = -1 Then Exit Sub
        For i = 0 To ListBox1.Items.Count - 1
            If ListBox1.GetSelected(i) = True Then
                For j = 0 To ListBox2.Items.Count - 1
                    If ListBox1.Items(i) = ListBox2.Items(j) Then
                        zjbd = True
                    End If
                Next
                If zjbd = False Then ListBox2.Items.Add(ListBox1.Items(i))
                zjbd = False
            End If
        Next