http://docs.webix.com/samples/15_datatable/04_editing/07_checkbox.html
How to get selected value
You can use something like next
$$("$datatable1").eachRow(function(id){
if (this.getItem(id).ch1) alert(id+" is checked");
})
Code will iterate through grid and check for which row checkbox is checked ( “ch1” - id of checkbox column )