How to check data input in datagrid

private void dataGridView1_CellValueChanged(object sender, DataGridViewCellEventArgs e)
{
  if (e.ColumnIndex >=0 && e.RowIndex >=0)
  {
    if (dataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Value != null)
    {
      if (dataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Value.ToString() != "")
      {
        if (float.Parse(dataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Value.ToString()) > 3.1)
        {                             
          dataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Value = null;
        }
      }
    }
  }
}