As a crestron programmer myself, I would specify a logarithmic guage with the output of the analog logic symbol (log with limits), and we can write simple+ code to weight the values if you really needed it. This avoids weighting it before it comes into the system. I think the easiest way to do this would be to buy a bridge rectifier and run directly into the analog input.
You can get one here
http://www.mouser.com/index.cfm?handler=displayproduct&l stdispproductid=279726&e_categoryid=236&e_pcodeid=58 301
My guess is that this device is simply used to show an incoming signal to "non-audio corporate types". Feel free to jump in here.
The main issue would be scaling your input to a 10v max level. You should decide at what voltage above .775volts you need. For example, if it monitors a console, you might need 26db of headroom above .775 V, which is 15.5 V. At 10 V, your guage would have 22 dB of headroom, probably sufficient for your use without tuning the gain. If you want a different gain structure, you would need to attenuate or gain the max level to 10 V and build your graphics around the level you set.
Let us know what you decide to do.