Well, it sounds like you have your bridge on a public node.
Hard to have 'selective control' that way.
Think of it a bit backwards.

I have dmr tg 91 set-up on 29999 for the last several months.
It's in rx only
Folks have been connecting and 'monitoring'.

If I wish to use it on 29285, in tx,
I can put a description on that server with the private node# ip, port for that direct connect on the other server. (rpt,conf)

1990 = radio@...:4569/1999,NONE ;29999 dmr

So I can still connect to that dmr bridge on the other server by using 1990 connection in what ever mode, but the node number is 1999 on the 29999 server.

1999 dmr bridge ->rx-> 29999 <-trx-> public connects
29285 <-> 1990(1999 on other server) private trx connect to my dmr bridge on other server.

hope this clears your thinking.

I actually have something like this on each of 5 servers even though each have there own dmr bridge, I can just use the connection of the others for my private trx connects. But i do not allow ASL to dmr on unmonitored high traffic dmr tg's. And I would encourage everyone to think about the implications of that.

Lots of control possibilities with this method. But there is always more than one way to skin that cat.

...mike/kb8jnm