【VBA】重複データを開かずに(外部参照で)転記する方法

Option Explicit
Sub TransferDuplicateData()
    Dim wbSource As Workbook, wsSource As Worksheet
    Dim wbTarget As Workbook, wsTarget As Worksheet
    Dim lastRowSource As Long, lastRowTarget As Long
    Dim i As Long, j As Long
    
    ' ソースワークブックを開く
    Set wbSource = Workbooks.Open("C:\path\to\source.xlsx")
    Set wsSource = wbSource.Sheets("Sheet1")
    lastRowSource = wsSource.Cells(wsSource.Rows.Count, 1).End(xlUp).Row
    
    ' ターゲットワークブックを取得
    Set wbTarget = ThisWorkbook
    Set wsTarget = wbTarget.Sheets("Sheet2")
    lastRowTarget = wsTarget.Cells(wsTarget.Rows.Count, 1).End(xlUp).Row + 1
    
    ' 警告オフ、画面更新停止
    Application.ScreenUpdating = False
    Application.DisplayAlerts = False
    
    For i = 2 To lastRowSource
        If IsDuplicate(wsTarget, wsSource.Cells(i, 1).Value) Then
            wsTarget.Cells(lastRowTarget, 1).Value = wsSource.Cells(i, 1).Value
            lastRowTarget = lastRowTarget + 1
        End If
    Next i
    
    ' ワークブックを閉じる
    wbSource.Close SaveChanges:=False
    Application.ScreenUpdating = True
    Application.DisplayAlerts = True
End Sub

Function IsDuplicate(ws As Worksheet, valueToCheck As Variant) As Boolean
    Dim lastRow As Long
    lastRow = ws.Cells(ws.Rows.Count, 1).End(xlUp).Row
    
    For j = 2 To lastRow
        If ws.Cells(j, 1).Value = valueToCheck Then
            IsDuplicate = True
            Exit Function
        End If
    Next j
    IsDuplicate = False
End Function