Access Another control which was in same level or in row

 function YourFunctionName(sender, args) {
                // Do not forget to add jquery in reference
                var SenderId = sender.id;
                //var SenderId = sender.get_element().id;
                //var SenderId =  sender.get_id();
                var RadTextBox1 = $("#" + SenderId).get(0);
                var RadTextBox2 = $("#" + SenderId.replace("RadTextBox1", "RadTextBox2")).get(0);
               // for telerik /radcontrols
                var RadTextBox2 = $telerik.findTextBox(SenderId.replace("RadTextBox1", "RadTextBox2"));

            }