Item calculation in Network maps

[kalvis.k]

Hi!
I`m monitoring few network switches with SNMP. Discovered items are : SwitchName:ifInOctets[Ethernet Routing Switch - Unit 1 Port 24].

On network map I`d like to make visual link and sum of "ifIn" and "ifOut" Octets on the link. I can`t find formula/macros,...

[Frederico]

How i can make a sum of this itens ??

On server i have:
eth0
eth1
eth1.100 (Vlan 100)
eth1.101 (Vlan 101)
eth1.102 (Vlan 101)

I need sum vlan traffic.

I tried create on host:

net.if.in[soma_link_operadora]...