SimCity4 - Commuting across region squares

I don't think there is going to be a solution to this, and it's just a quirk of the game, but more wondering if anyone knows of a mod to combat this. I will try and explain as clearly as possible.

You have two or more adjacnet cities that are extablished and you then create a new city that is again adjacent to an existing city - so you have a group of ajacnet cities....

If you create a new link between two of these cities via either ferry, rail or road you then have to go into each of the cities, save and exit the city for the population to realise they can commute into, or through that city (I hope that makes sense).  If you don't enter, save and exit each city the new (e.g.) train line will have "0" commuters, once you have done the whole exit and enter process, that number will jump to what ever it will become, 2300 or 10000 commuters or what ever.

I was wondering if there is a way of just connecting the city and the population to realise they can commute between cities without the whole jumping in and out to make them start moving.

Thanks in advance if that question makes any sense at all...