Mimic how opportunity amount is calculated. (kinda)

Hello

So I want to use a calculated field to calculate different kinds of weights. The problem is that I need to get the data from a detail on this page with calculated fields.

It goes like this

-| Shipments Page

---| CBM (field on shipment page)

---| Volume Weight (field on shipment page)

---| Total Value (field on shipment page)

---| Containers (detail on shipment page)

------| Dimensions (field on the detail on the shipment page)

------| Value (field on the detail on the shipment page)

If that makes sense so I need to get the data off of the detail that is on the page using client side code preferably (javascript), so I can set up the calculated field. So there can be many containers on this shipment page and I need to be able to sum all of it up and calculate it.

Much like how opportunity amount is calculated off of opp products (which is a detail) I need to do the same but I am not sure how to reference the detail in client side code. Is there anyway to do this? e.g. like how on the opportunity page the opportunity amount is set using the opportunity products which is a detail on the page.