With List2
    For i = 0 To .ListCount - 1
        For j = 0 To List3.ListCount - 1
            If .List(i) = List3.List(j) Then
                .RemoveItem i
            End If
        Next j
    Next i
End With

删除两个列表框相同项

删内容的那个列表框要倒序查找删。

For j =  List3.ListCount - 1 to 0 step -1

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