I accomplished it by adding an Input Channel to one of the devices with “Calculated real” type. In my case is channel 41.
I entered there a formula, for example: Val(615) * Val(32),
being 615 and 32 the numbers of the channels coming from different devices.
Afterwards, in Scheme Editor I put a Dynamic text indicating to show the value of input channel 41.
This worked out for input channels from different or from the same device.
Thank you for support.