DI doesn't work this way. If you have new functionality, then you have to write code. So, if you add a new company and that has specific logic, then you will have to write that logic - DI is not a magic bullet. What it would do, is save you having to write any logic to hook it up to your UI, for instance.
If you're going to do this, then I'd suggest that you read a few artioles here on Code Project. This[^] is a good place to start. Beyond that, I'd also consider investigating MEF.
*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington