On load of Child table row

How can I catch on load of Child table row?

When a user clicks on a row, I want to catch this event a populated a value.

Hi, please check frappe/public/js/frappe/form/grid_row.js

add_open_form_button: function() {
		var me = this;
		if(this.doc && !this.grid.df.in_place_edit) {
			// remove row
			if(!this.open_form_button) {
				this.open_form_button = $('<a class="close btn-open-row">\
					<span class="octicon octicon-triangle-down"></span></a>')
					.appendTo($('<div class="col col-xs-1 sortable-handle"></div>').appendTo(this.row))
					.on('click', function() { me.toggle_view(); return false; });

				if(this.is_too_small()) {
					// narrow
					this.open_form_button.css({'margin-right': '-2px'});