Edit tracking company for an item already added

It would be useful in my case. I live in Canada and ship form the US on USPS. Once it crosses the border I have to copy the tracking number and make a new entry for Canada Post. This would be great also if I don't happen to know the carrier.

This would also be great for shippers who transfer packages to USPS for the last leg of the delivery (ie. FedEx Smartpost, UPS Mail Innovations, DHL) - especially if Posted could spot the handoff and switch the carrier automatically.