Vba 5941错误请求的集合成员不存在Word宏

大家好。我远离程序员，但是我需要帮助找出这个VBA脚本的错误。它在维修订单表格的word文档中运行。其目的是为每次打印增加一个订单号。计数器更新.txt文件以确定下一个需要打印的数字。就我的理解而言。代码如下

Sub serialNumberPrint()
'
' SerialNumber Macro
'
'
Dim Message As String, Title As String, Default As String, NumCopies As Long
Dim Rng1 As Range

' Set prompt.
Message = "Enter the number of copies that you want to print"
' Set title.
Title = "Print"
' Set default.
Default = "1"

' Display message, title, and default value.
NumCopies = Val(InputBox(Message, Title, Default))
SerialNumber = System.PrivateProfileString("C:\Users\GaleR\Documents\SettingsSerial.Txt", _
"MacroSettings", "SerialNumber")

If SerialNumber = "" Then
    SerialNumber = 1
End If

Set Rng1 = ActiveDocument.Bookmarks("SerialNumber").Range
Counter = 0

While Counter < NumCopies
    Rng1.Delete
    Rng1.Text = Format(SerialNumber, "000#")
    ActiveDocument.PrintOut
    SerialNumber = SerialNumber + 1
    Counter = Counter + 1
Wend

'Save the next number back to the Settings.txt file ready for the next use.
System.PrivateProfileString("C:\Users\GaleR\Documents\SettingsSerial.txt", "MacroSettings", _
        "SerialNumber") = SerialNumber

'Recreate the bookmark ready for the next use.
With ActiveDocument.Bookmarks
    .Add Name:="SerialNumber", Range:=Rng1
End With

ActiveDocument.Save


End Sub

---

我束手无策，不知道如何继续。我事先为我的知识不足表示歉意，但确实需要帮助。

错误告诉您文档中不存在书签序列号。如果您选择文档（或模板）中的位置并插入具有该名称的书签，应该可以解决问题。

您能否详细说明预期行为和实际输出是什么？脚本失败了，输出了错误的信息，还有其他原因吗？

 Set Rng1 = ActiveDocument.Bookmarks("SerialNumber").Range