我在DataGridView添加了一列DataGridViewComboBoxColumn列名units，为其建立一个模板
public class classComboData
    {
        private string m_display = string.Empty;
        private string m_value = string.Empty;

        public classComboData(string display, string value)
        {
            this.m_display = display;
            this.m_value = value;
        }
        public string Display
        {
            get { return this.m_display; }
            set { this.m_display = value; }
        }
        public string Value
        {
            get { return this.m_value; }
            set { this.m_value = value; }
        }

    }
//读取配置文件，取得所有的单位名称和其ID号
XmlNodeList unitName = mainfrm.class_ReadxmlDB.GetNodeList((int)classReadXML.AllXMLFile.unitsName);
if (unitName != null && unitName.Count > 0)
{
   DataGridViewComboBoxCell cellSex = new DataGridViewComboBoxCell();
   for (int i = 0; i < unitName.Count; i++)
   {
       string displayName = unitName.Item(i).Attributes["UnitName"].Value.ToString();
       string displayValue = unitName.Item(i).Attributes["ID"].Value.ToString();
//将单位名称添加到DataGridViewComboBoxCell
       cellSex.Items.Add(new classComboData(displayName, displayValue));
    }
       cellSex.DisplayMember = "Display";
       cellSex.ValueMember = "Value";
       units.CellTemplate = cellSex;   //设置列DataGridViewComboBoxColumn列名units的模板
       unitName = null;
 }
怎样再窗体加载时设置此列的默认值？
请各位帮帮忙！！！！！！！！！！！！！！