How to build calculated items automaticaly with items in special Applications

[simox]

It is a special request. I wanna monitoring a group of routers, when they all have hundreds of interfaces and all interface applications have been found with the SNMP template.
Some of the interfaces are upload ports, and I just want to sum the PACKETS INBOUND and PACKETS OUTBOUND of all upload ports of a router, then graph the two items.
In fact I have made the two calculated items by hand, but its very hard. The upload interfaces have different #IFNAME. First I have to find the {#SNMPINDEX} of all upload interfaces, then build calculated items by hand, then graph them by hand, then next router, but there're too many routers!!!!!

I want to build a template or something else that can help to build this kind of calculated items automaticaly. Any professor has expresence of this request? Iv serached a lot but have no idea about this.
Thanks in advance.

PS: the upload interfaces have similar #IFALIAS, which contain a special String to difference between other interfaces.

[Hamardaban]

Aggregate item work with the same keys for the hosts (in group). And here is a different task - the keys are different within the same host.
Such problems arise regularly-I do not know the solution yet. At the conference, future changes in formulas were presented and something similar was mentioned.