Onclick for custom module doctype in core module form - how to trigger?

ERPNext
1

Onclick function for field inside a table of custom module doctype is not triggered inside “Customer” doctype of core erp module. Not able to trigger using jquery either. Please help.

2
  1. Share your use case
  2. Share the code you have tried, so someone can try to help
3

This is the code that I have used:

frappe.ui.form.on("Customer", {
   //custom_field belongs to custom_doctype created inside 'custom_module'
   //custom_field is a column inside a table(custom_doctype) in this form
	  custom_field: function() {
		alert('Changed!');
	  },