Generate some custom fields on Delivery note While Filling Items from Get Items

ERPNext
,
1

Hi,

I have a scenerio where I created two master field on sales order named style and brand.

Now, I need to pull this style and brand on delivery notes item level while I pull the data from Sales Order.

I have write down a script to puopulate this feilds as below:

function populate_so_related_fields(frm) {

if (!frm.doc.items || !frm.doc.items.length) return;

frm.doc.items.forEach(row => {

    // Must be mapped from Sales Order
    if (!row.sales_order) return;

    if (!row.custom_po_no) {
        frappe.call({
        method: "getPOandStyle",
    args: {
        sales_order: row.sales_order
    },
      callback: function (r) {
                if (r) {
                    frappe.model.set_value(row.doctype, row.name, "custom_po_no", r.message.po_no);
                    frappe.model.set_value(row.doctype, row.name, "custom_style", r.message.custom_style);
                     frappe.model.set_value(row.doctype, row.name, "custom_brand", r.message.custom_brand);
                }
            }
       
    })

}
})
}

Now I am wondering on which event I will call this function.

any idea?