Handsontable : how to change cell value in render function-open source projects handsontable/handsontable

I have similar code:

$(document).ready(function () {
    var data = @Html.Raw(ViewBag.Data);

function sumPreviousValues(instance, td, row, col, prop, value, cellProperties) {
  Handsontable.renderers.TextRenderer.apply(this, arguments);
    td.val = 'SUM SEVERAL PREVIOUS CELLS';
}

     container = document.getElementById('example1'),
      settings1 = {
        data: data,
        colHeaders: @Html.Raw(ViewBag.TableHeader),
        cells: function (row, col, prop) {
            var cellProperties = {};

            if (col == 16) {
                cellProperties.renderer = sumPreviousValues;
            }
    return cellProperties;
        }
      },

    hot = new Handsontable(container,settings1);
    hot.render();

The key is to modify the function sumPreviousValues()

But I dont know how to access the td value ? and if it is possible to access other cells’ value like td[index]. Any idea? I didn’t find options in documentation.

Thank you