How to perform calculation if user change value of cell in data grid view C# using unbound data

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C#

i have program which add all the default values of first four rows and show total in 5th row.
i have requirement that if user change the value of any row from first 4, it should automatically update in 5th row. like in excel sheet if we change the value of any cell all the connected cell updates immediately

What I have tried:

dataGridView1.Rows[4].Cells[1].Value = (int)double.Parse(dataGridView1.Rows[0].Cells[1].EditedFormattedValue.ToString())
                                                       +double.Parse(dataGridView1.Rows[1].Cells[1].EditedFormattedValue.ToString())
                                                       +double.Parse(dataGridView1.Rows[2].Cells[1].EditedFormattedValue.ToString())
                                                       +double.Parse(dataGridView1.Rows[3].Cells[1].EditedFormattedValue.ToString());