Group two monitor points into one graph

Hello,

I have created a custom dashboard, all works fine. I am monitoring system.net on multiple servers, but would like a separate graph to show the sum of all system.net values.

This is what I have at the moment:

These display two graphs for sent traffic on ETH0 on each server, but I would like another single graph that sums both of these into a single graph.

Is this possible?

Thanks in advance!