Hi Freilicht
A very fair question. Consider the two B-Stations, in this case, as a 'master' and a 'slave'. The master has the DMX output connected to the dimmer. The other will be connected to that master via the network. Programming now has to be made in such a way, that pressing button 1, for instance, on the Master, will start playback 1. Then you can make a Playback actionlist, and create and action that sends a button light/colour change message to both the itself and the slave. On the slave, you make a button 1 action that sends the master a message to start playback one. In this case both buttons will do and behave exactly the same.
Have a play with this.
And if you need more information, let us know. Then we can make you a backup file with an example.
Also, on our downloads page, under miscellaneous, we have a B-Station2 applications package with a number of examples, including their backups, for you to use and adapt to your situation. Perhaps something in there can be of use. Or gets you inspired.
Cheers,