Summarize a column

Hello. How are they? Can you help me please.
I have an application called Orders Puerto Med, which is used to place restaurant orders and take orders. The application has a form with a reference from another form. The main form contains shipping data such as payment method, address, name, contact, among others. The reference form has data of the dish to order, quantity, price and subtotal (quantity * price). I want there to be a column in the main form that is called total (which would be the total of the entire order) and shows the total of all the items entered.

Name of the main form sheet: “Form”
Name of the referenced form sheet: “Detail”
Name of the column that is the key between Form and Detail: “Order Code”
Column in the referenced form sheet that I want to add “Total”

Thanks a lot!!
Gene