Or perhaps you are thinking about creating a carrier service, so Shopify will fetch shipping prices in realtime? That's for people on Shopify Plus plans, which costs $2k/mo+.
Actually, that's not quite true! There's a wholly undocumented option for non-plus merchants to get the carrier service feature enabled on their account for a monthly fee of something like $25. They have to reach out to support.
Everything with Shopify is like this. Great for consultants who have already internalized all this knowledge, sure.