如何以编程方式显示或隐藏Outlook信封图标？

Sub ToggleEnvelope()
    Dim olApp As Outlook.Application
    Dim olNs As Outlook.NameSpace
    Dim olFolder As Outlook.MAPIFolder
    Dim olItem As Outlook.MailItem
    Dim strFolder As String
    
    ' 指定要操作的文件夹路径
    strFolder = "Inbox"
    
    ' 获取Outlook应用程序对象
    Set olApp = Outlook.Application
    
    ' 获取当前用户的默认文件夹集合
    Set olNs = olApp.GetNamespace("MAPI")
    
    ' 获取指定文件夹
    Set olFolder = olNs.GetDefaultFolder(olFolderInbox)
    
    ' 遍历文件夹中的所有邮件
    For Each olItem In olFolder.Items
        ' 切换信封图标的显示和隐藏
        If olItem.UnRead = True Then
            olItem.UnRead = False
        Else
            olItem.UnRead = True
        End If
    Next olItem
    
    ' 清理对象变量
    Set olItem = Nothing
    Set olFolder = Nothing
    Set olNs = Nothing
    Set olApp = Nothing
End Sub