How to set SelectedIndex in DataGridViewComboBoxColumn

DataGridViewComboBoxColumn ColumnPage = new DataGridViewComboBoxColumn();
ColumnPage.DefaultCellStyle.NullValue = "Medium";

 

        DataGridView1.Columns.Insert(11, 수동관계)
        수동관계.Items.AddRange("100", "90", "80", "70", "60", "50", "40", "30")
        수동관계.DisplayMember = "100"
        수동관계.ValueMember = "100"
        수동관계.DefaultCellStyle.NullValue = "100"