Sub test()
Dim dicObj As Object
Dim i&, iLastRow&
Dim Kniga1_List1 As Worksheet
  Set Kniga1_List1 = Workbooks("Книга1.xls").Worksheets("Лист1")
  Set dicObj = CreateObject("scripting.dictionary")
      dicObj.comparemode = 1
With Sheets("Лист1")
  For i = 5 To .Cells(.Rows.Count, "C").End(xlUp).Row
    dicObj.Item(.Cells(i, "C").Value) = 0
  Next i
End With
With Kniga1_List1
   For i = 4 To .Cells(.Rows.Count, "C").End(xlUp).Row
     If Not dicObj.exists(.Cells(i, "C").Value) Then 'если нет слова, то добавляем его в словарь
            dicObj.Item(.Cells(i, "C").Value) = 0
         iLastRow = Cells(Rows.Count, 1).End(xlUp).Row + 1
         .Range("A" & i & ":C" & i).Copy Cells(iLastRow, 1)
      End If
   Next i
End With
End Sub

Sub test()
Dim dicObj As Object
Dim i&, iLastRow&
Dim Kniga1_List1 As Worksheet

Set Kniga1_List1 = Workbooks.Open("Книга1.xls").Worksheets("Лист1")  'Open добавлено мной
Set dicObj = CreateObject("scripting.dictionary")
dicObj.comparemode = 1
With Sheets("Лист1")
For i = 5 To .Cells(.Rows.Count, "C").End(xlUp).Row
dicObj.Item(.Cells(i, "C").Value) = 0
Next i
End With
With Kniga1_List1
For i = 4 To .Cells(.Rows.Count, "C").End(xlUp).Row
If Not dicObj.exists(.Cells(i, "C").Value) Then 'если нет слова, то добавляем его в словарь
dicObj.Item(.Cells(i, "C").Value) = 0
iLastRow = Cells(Rows.Count, 1).End(xlUp).Row + 1
.Range("A" & i & ":C" & i).Copy Cells(iLastRow, 1)
End If
Next i
End With
Workbooks("Книга1.xls").Close False 'добавлено мной
End Sub

Sub ClearStr()
Dim lngI As Long

    ClearWord = "ааа, ббб, ввв"
    
For lngI = Cells(Rows.Count, 3).End(xlUp).Row To 5 Step -1 
     If InStr(ClearWord, Cells(lngI, 3)) > 0 Then Rows(lngI).ClearContents
Next lngI
End Sub

         .Range("A" & i & ":C" & i).Copy
         Cells(iLastRow, 1).PasteSpecial xlPasteValues

Application.ScreenUpdating = False

Application.ScreenUpdating = True

Application.FileDialog(msoFileDialogFilePicker)

    ' диалог выбора файла 
Dim FD As FileDialog
Dim iFileName As String
Dim iShortFileName As String
Set FD = Application.FileDialog(msoFileDialogFilePicker)
    With FD
        .Filters.Clear  'удаляет предопределенные фильтры
        .Filters.Add "Microsoft Excel files", "*.xls"
        .Filters.Add "All files", "*.*"
        .AllowMultiSelect = False
        .InitialFileName = ThisWorkbook.Path
        .Title = "Выберите нужный файл "
        .ButtonName = "Открыть"
        If .Show = False Then
            MsgBox "Вы не указали нужный файл!", 48, "Ошибка"
            Exit Sub
        Else
            iFileName = .SelectedItems(1)
            iShortFileName = Right(.SelectedItems(1), Len(.SelectedItems(1)) _
                        - InStrRev(.SelectedItems(1), "\"))
        End If
    End With
    Set FD = Nothing
       'открываем книгу в режиме только чтение
      Workbooks.Open Filename:=iFileName, UpdateLinks:=False, ReadOnly:=True

      '........
      Workbooks(iShortFileName).Close SaveChanges:=False '(True)

Workbooks.Open Filename:="Полный путь\Книга1.xls", UpdateLinks:=False, ReadOnly:=True

Workbooks("Книга1.xls").Close SaveChanges:=False '(True)