【Excel】VBAマクロで複数シートに同じ処理を繰り返す（同じ作業を特定シートまで：ブック全体など）方法

Sub SheetSum()
    Dim ws As Worksheet
    Dim lastRow As Long
    Dim sumResult As Double
    For Each ws In ThisWorkbook.Sheets
        lastRow = ws.Cells(ws.Rows.Count, "C").End(xlUp).Row
        sumResult = Application.WorksheetFunction.Sum(ws.Range("C2:C" & lastRow))
        ws.Range("D1").Value = sumResult
    Next ws
End Sub

Sub SheetAverage()
    Dim ws As Worksheet
    Dim i As Integer
    Dim lastRow As Long
    Dim averageResult As Double
    For i = 1 To 3
        Set ws = ThisWorkbook.Sheets(i)
        lastRow = ws.Cells(ws.Rows.Count, "C").End(xlUp).Row
        averageResult = Application.WorksheetFunction.Average(ws.Range("C2:C" & lastRow))
        ws.Range("D1").Value = averageResult
    Next i
End Sub