//add new column for calculate
                var isEdited = new DataGridViewTextBoxColumn();
                var txtcell = new DataGridViewTextBoxCell();
                isEdited.CellTemplate = txtcell;
                isEdited.ValueType = typeof(double);
                isEdited.Name = "Summ";
                isEdited.HeaderText = "Summ";
                isEdited.Visible = true;
                isEdited.Width = 80;
                //MessageBox.Show("" + dataGridView1.ColumnCount);
                dataGridView1.Columns.Add(isEdited);
                //MessageBox.Show("" + dataGridView1.ColumnCount);
                dataGridView1.CommitEdit(DataGridViewDataErrorContexts.Commit);
                dataGridView1.EndEdit();
                //set хащалбак = value3*value4
                for (int i = 0; i < (dataGridView1.RowCount-1); i++)
                {
                    dataGridView1.Rows[i].Cells[4].Value = TestLibrary.Class1.SumFunc(Convert.ToDouble(dataGridView1.Rows[i].Cells[3].Value), Convert.ToDouble(dataGridView1.Rows[i].Cells[4].Value));
                }