VUMeter change function?

Is there any documentation/example how to get vumeter values changes methods getting active on a selected channel?

Can you explain more detailed what you are trying to do?
The level meters have some settings in the preferences. But they are on different positions.

Im trying to get the VU data, like the most mixer consoles. MCU, HUI, EuCON etc.
MCU does not have it for all channel types. Missing input and output. But It would also be useful for ControlRoom.