Math operations on graph and aggregation graph

[grzesiek]

Hello
I try use Cacti 1.1 to draw graph from 3 device (two Linux and one switch). My goal is sum two Linux bandwidth and subtraction this sum from switch bandwidth.
I know how to do math operation, I create CDEF like "b,d,+,f,-" and add this CDEF to graph via modify used template. Line of my CDEF is draw, but I don't have label (GPRINT) with the value of this line and I don't know how do it.
Can you help me with this?