Property to monitor standby comm/nav frequency?

[D-ECHO]

Hi,
while modelling the SL30 for flightgear, I came across the "monitor" function, it makes you listen to the frequency selected on sby, while still being able to talk and listen to active freq (monitored frequency is muted while there is RX on active frequency). I wondered whether there is such a function available in the flightgear comm system?
Regards and thanks in advance
D-ECHO