How to get the cell value of a nested data grid using JavaScript

You can try this:
1. Put a checkbox.
2. On clicking of checkbox below JQuery code will give you the cell value:

$(ctrl).parents('tr').children().filter(function(index) {
                return index == 1;
            }).html()

Note: I've considered that the required cell is imediately after the checkbox (hence index = 1). Also you can use any control in place of checkbox.