【近似曲線】Excelを使って計算式を元にデータを予測する方法！

Sub 近似曲線の数式を取得()
'変数の型を宣言
    Dim x_ax As String, y_ax As String
    Dim grf_formula As String
    Dim a As Single, b As Single, c As Single
    'データ範囲を指定する（やるのはここだけ）
    x_ax = "A2:A11"
    y_ax = "B2:B11"
    'グラフ（散布図）を挿入する
    ActiveSheet.Shapes.AddChart2(-1, -4169).Select
    With ActiveChart
        '指定したデータでグラフ作成
        .Parent.Name = "sample_grf"
        .SeriesCollection.NewSeries
        With .FullSeriesCollection(1)
            .XValues = ActiveSheet.Name & "!" & x_ax
            .Values = ActiveSheet.Name & "!" & y_ax
        End With
    End With
    'グラフに近似曲線を追加する
    With ActiveChart.SeriesCollection(1)
        .Trendlines.Add
        .Trendlines(1).Select
    End With
    '近似曲線の種類を指定する
    With Selection
        .Type = xlPolynomial
        .Order = 2
    End With
    Selection.DisplayEquation = True
    '近似曲線の式の桁数を指定する
    ActiveSheet.ChartObjects("sample_grf").Activate
    With ActiveChart.SeriesCollection(1).Trendlines(1).DataLabel
        .NumberFormat = "#,##0.000000_ "
    End With
    'グラフの近似式をリフレッシュ
    ActiveSheet.ChartObjects("sample_grf").Activate
    ActiveChart.Refresh
    'グラフの近似式を取得する
    With ActiveChart.SeriesCollection(1).Trendlines(1).DataLabel
        grf_formula = .Text
    End With
    ActiveSheet.ChartObjects("sample_grf").Delete
    split_formula = Split(grf_formula, " ")
    a = split_formula(2)
    b = split_formula(4) & split_formula(5)
    c = split_formula(7) & split_formula(8)
    '数式&係数をセルに書き出す
    Cells(1, 4) = grf_formula
    Cells(2, 4) = "a="
    Cells(2, 5) = a
    Cells(3, 4) = "b="
    Cells(3, 5) = b
    Cells(4, 4) = "c="
    Cells(4, 5) = c
End Sub

Sub 文字を置き換えて連続コピー()
Dim rng As String
Dim i As Long
Dim top As Long
Dim bottom As Long

top = Cells(Rows.Count, 2).End(xlUp).Row
bottom = Cells(Rows.Count, 1).End(xlUp).Row

rng = Cells(1, 4)
    rng = Replace(rng, "x2", "*A12^2") 'A12の部分は指定する
    rng = Replace(rng, "x", "*A12") 'A12の部分は指定する
    rng = Replace(rng, " ", "")
    rng = Replace(rng, "y", "")
    Cells(top + 1, 2) = rng
    
    Cells(top + 1, 2).AutoFill Destination:=Range(Cells(top + 1, 2), Cells(bottom, 2))
End Sub