So, you have a library for Drivers and another for Items, and one is linked to the other with what kind of link-to-entry field? One-to-many or many-to-many? Which is linked to which? How do identify an item? Do you key in an ID or pick from the list of links or pick from a radio-buttons field or what? How do you identify a driver (same choices)?
Weights can be combined by summing them, averaging them, or otherwise. How do you want them combined? How would you combine dimensions? How do you store dimensions? 3 fields of length, width, & height or depth?
If things are simple, using the entries list screen can allow you to aggregate, subtotal groups, filter certain categories of entries, even chart them, etc. If things are more complicated, you can use scripting to combine things, store the combined results, etc.
Ideally, you could spell out your libraries, your fields & field types, and give whatever other info might help us to help you.