How to allow user to group records on a table?

I am writing a web based ERP for bus companies. There is a section on the system where the user should be able to divide a route into segments that can (or not) be owned by different bus companies.

Right now it looks like this:

On the Company column, there is a combobox with the possible companies, and basically the user selects the company for each stop, but as you can see, they repeat (and there are routes with ~40 stops that have one company for the first 20 and another for the rest).

One thing I am currently doing is that, lets say the user enters "Tornado" on the 1st stop and Expreso on the 20th stop, if this happens, I am auto-selecting Tornado for the 2nd to the 19th stop. But I think is not super clear for the user.

Can you suggest a way to make this easier for the users?

Thanks!