' 文字列の一部を置換え(Insert)
Sub ki137()
    Cells(12, 6).Select
    ActiveCell.Characters(4, 3).Insert "aaa"
     Cells(12, 2).Select
End Sub


Sub ki137a()
    Cells(12, 6).Select
    ActiveCell.Formula = "ABCDEFGHIJKLMN"
    Selection.Font.Size = 12
    Cells(12, 2).Select
End Sub