How to capture onHold time in incident form ServiceNow

u_updateTaskAging();
    function u_updateTaskAging() {
     var elapsedTime = 0;
     var aging="";
     var gr = new GlideRecord('incident');
     gr.addEncodedQuery('stateNOT IN7,8');
     gr.orderByDesc("sys_created_on");
     gr.query();
     while (gr.next()) {
         var gr1 = new GlideRecord("metric_instance");
         gr1.addEncodedQuery("duration!=NULL^value=On Hold^definition=35f2b283c0a808ae000b7132cd0a4f55^id=" + gr.sys_id);
         gr1.query();
         if (gr1.next()) {
             aging="";
             elapsedTime = (gs.dateDiff(gr1.start, gr1.end, true)) / 60 / 60 / 24;
             if (elapsedTime <= 6) {
                 aging = '0-6days';
             }
             if ((elapsedTime > 6) && (elapsedTime <= 30)) {
                 aging = '7-30days';
             }
             if (elapsedTime > 30) {
                 aging = '>30days';
             }
             gr.setWorkflow(false); // Skip any Business Rules
             gr.autoSysFields(false); // Do not update system fields
             gr.u_aging_onhold = aging;
             gr.update();
         }
     }
 }