DataTable workTable = new DataTable("Purchase Items"); DataColumn workCol = workTable.Columns.Add("ID", typeof(Int32)); workTable.Columns.Add("UnitPrice", typeof(Double)); workTable.Columns.Add("Qty", typeof(Int32)); workTable.Columns.Add("Total", typeof(Double)); workTable.Columns.Add("Discount", typeof(Double)); workTable.Columns["Total"].Expression = "UnitPrice*Quantity"; workTable.Columns["Discount"].Expression = String.Format("Total*{0}",Discount); dataGridView1.DataSource = workTable; dataGridView1.Update();