Excelが重いときの原因と軽くする方法

Option Explicit

' シートごとに「重くなる原因」を数えて、新しいシートに一覧にする（数えるだけで、何も変えない）
Sub CheckHeavySheets()
    Dim wb As Workbook, ws As Worksheet, out As Worksheet, r As Long
    Dim lastR As Range, lastC As Range, f As Range, c As Range, vol As Long

    Set wb = ActiveWorkbook
    Set out = wb.Worksheets.Add(After:=wb.Sheets(wb.Sheets.Count))
    out.Range("A1:E1").Value = Array("シート", "条件付き書式のルール", _
        "Excel が使っている範囲の最後", "データの最後", "揮発性関数を使った数式")
    r = 2
    For Each ws In wb.Worksheets
        If Not ws Is out Then
            out.Cells(r, 1).Value = ws.Name
            out.Cells(r, 2).Value = ws.Cells.FormatConditions.Count
            With ws.UsedRange
                out.Cells(r, 3).Value = ws.Cells(.Row + .Rows.Count - 1, .Column + .Columns.Count - 1).Address(False, False)
            End With

            Set lastR = ws.Cells.Find("*", LookIn:=xlFormulas, SearchOrder:=xlByRows, SearchDirection:=xlPrevious)
            Set lastC = ws.Cells.Find("*", LookIn:=xlFormulas, SearchOrder:=xlByColumns, SearchDirection:=xlPrevious)
            If lastR Is Nothing Then
                out.Cells(r, 4).Value = "（空）"
            Else
                out.Cells(r, 4).Value = ws.Cells(lastR.Row, lastC.Column).Address(False, False)
            End If

            vol = 0
            Set f = Nothing
            On Error Resume Next                 ' 数式が1つもないシートではエラーになるため
            Set f = ws.UsedRange.SpecialCells(xlCellTypeFormulas)
            On Error GoTo 0
            If Not f Is Nothing Then
                For Each c In f
                    If IsVolatile(c.Formula) Then vol = vol + 1
                Next c
            End If
            out.Cells(r, 5).Value = vol
            r = r + 1
        End If
    Next ws

    out.Columns("A:E").AutoFit
    MsgBox "結果を「" & out.Name & "」シートに書き出しました。", vbInformation
End Sub

Private Function IsVolatile(ByVal fm As String) As Boolean
    Dim fn As Variant
    fm = UCase(fm)
    For Each fn In Array("OFFSET(", "INDIRECT(", "NOW(", "TODAY(", "RAND(", _
                         "RANDBETWEEN(", "RANDARRAY(", "CELL(", "INFO(")
        If InStr(fm, fn) > 0 Then IsVolatile = True: Exit Function
    Next fn
End Function