How to multiple two values with field type select

Good day guys.
I got stucked at an issue andI really need your help. I want to multiple two child table columns with field type select. Column A% by ColumnB when a value in COLUMNA is selected . below is my code
frappe.ui.form.on(“Child Table”, {
amount: function (frm, cdt, cdn) {
var d = locals[cdt][cdn];
frappe.model.set_value(cdt, cdn, “vat_amount”, d.amount * (d.vat_rate/100));
},
vat_rate: function (frm, cdt, cdn) {
var d = locals[cdt][cdn];
frappe.model.set_value(cdt, cdn, “vat_amount”, d.amount * (d.vat_rate/100));
},

Hi @lubem,

Please check it and apply it.

Then reload and check it.

Thank You!