Capture the total amount across all billing periods for the entire duration of contract in SO

I need to capture the total amount across all billing periods for the entire duration of the contract in the sales order total on the header. For example, assume there are five billing periods. I manually override the billing amounts for the first three periods to 200, 300, and 500 using Edit Recurring Billing, and the last two periods use the default price from the price list, say 100 each.

I want to calculate and display the total recurring billing amount for all five periods: 200 + 300 + 500 + 100 + 100= 1200. Same needs to be done for other lines having recurring billing. In addition, if there is any one-time sale price on the order, that amount should also be included in the total.