Fetch from Custom DocType

does the fetch / custom script cur_frm.add_fetch only work with standard docs and not with custom docs?
I have been trying to fetch data from a new doctype to salaryslip but the data does not get fetched.
code used:

frappe.ui.form.on(‘Salary Slip’, {
refresh(frm) {

Use this, and modify accordingly

frappe.ui.form.on("Inquiry", {
"refresh": function(frm, cdt, cdn) {
    var d = locals[cdt][cdn];
        frm.add_custom_button(__("Create Sales Order"), function() {
            frappe.new_doc('Sales Order', {
                "customer": cur_frm.doc.company_name,
                "inquiry_no": cur_frm.doc.name

thanks but it doesnt work for scenario i mentioned :frowning:

Is there any link field in your salary slip doctype from your custom doctype?

No link field.

This is the code i tried:
frappe.ui.form.on(“Inquiry”, {
“refresh”: function(frm, cdt, cdn) {
var d = locals[cdt][cdn];
frm.add_custom_button(__(“Create Salary Slip”), function() {
frappe.new_doc(‘Salary Slip’, {
“choice”: cur_frm.mess.choice,
“cnic”: cur_frm.employee.cnic

Instead of Inquiry, use your custom doc name

still not working :frowning: