Like Nico said, this function is very rare nowadays..
I don't own RTB2000 so cannot check, but on Siglent scopes I have, you can achieve something similar with Pattern trigger.
On them you can select to trigger on 2 analog channels with a logic function (AND or OR).
That way scope will trigger when, for instance, both signals have a rising edge at the same time (actually within user defined time window). If signals are not correlated in frequency, there will be many moments where that is true.
You can also experiment with OR, which in a way is alternate trigger. Here scope will trigger on any edge on any of channels ..
If I remember correctly, RTB2000 should have similar trigger mode.
Maybe try to experiment with that. Check manual for details..
Best,