Private Sub Worksheet_BeforeDoubleClick(ByVal Target As Range, Cancel As Boolean)
If InStr(Target.Value, "⇒") = 0 Then
Target.Value = Target.Value & "⇒"
ElseIf Right(Target.Value, 1) = "⇒" Then Target.Value = Target.Value & "予定"
ElseIf Right(Target.Value, 2) = "予定" Then Target.Value = Replace(Target.Value, "⇒予定", "⇒未定")
ElseIf Right(Target.Value, 2) = "未定" Then Target.Value = Left(Target.Value, Len(Target.Value) - 2)
End If
End Sub