dataGridView动态绑定问题：如何将默认的TEXT文本列类型转换成DataGridViewImageColumn列类型呢？

部分代码如下： 
DateTime tmp = new DateTime(DateTime.Now.Year, DateTime.Now.Month, 1).AddMonths(1).AddDays(-1);
            int monthDays = tmp.Day;
            this.dataGridView1.ColumnCount = monthDays + 4;
            for (int i = 0; i < monthDays; i++)
            {
                string td = DateTime.Now.Year.ToString() + "-" + DateTime.Now.Month.ToString() + "-";
                td += (i + 1).ToString();                string s = DateTime.Parse(td).DayOfWeek.ToString(); 
                dataGridView1.Columns[i + 3].Name = (i + 1).ToString()+"("+ s+")";
            }请问我添加的这些列的类型怎么转换成:DataGridViewImageColumn