Need help in fetching data

Frappe Framework Custom Script
12

Hi @Jitendra_Khatri1 @shivkumar @KanchanChauhan @Nick , what I want is a javascript handler that allows me to call add_fetch() after my tcno field loads ( which is linked with the item module ) , both item doc and Tc doc have the same field cmill , I tried to accomplish with the help of @shivkumar with this code , but this is not working , please someone help me ,

frappe.ui.form.on("TC", "onload", function(frm, cdt, cdn){
  if (cur_frm.doc.__islocal && cur_frm.doc.item){
    frappe.call({
      "method": "frappe.client.get_value",
      "args": {
         "doctype": "Item",
         "filters": cur_frm.doc.item,
         "fieldname": "cmill"
       },
      "callback": function(res){
        if (!res.exc){
          cur_frm.set_value("cmill", res.message.cmill);
        }
      }
    });
  }
});