Calculating Range of keys

[ThatITguyMike]

Hi all,
I am semi new to Zabbix and I can't seem to figure out this issue. I am trying to calculate total traffic across my core switch. I used a discovery rule to find the interfaces and there bandwidth. But now I need to calculate all of them together.

I tried making the calculated time in the discovery rule but it never worked. Can I make a range of calulations? For example:

last(CORE.Int.locIfInBitsSec.["1-208"])
+last(CORE.Int.locIfOutBitsSec.["1-208"])

Currently I am only able to get this to work by adding each interface to the formula.

last(CORE.Int.locIfInBitsSec.["1"])
+last(CORE.Int.locIfOutBitsSec.["1"])
+last(CORE.Int.locIfInBitsSec.["2"])
+last(CORE.Int.locIfOutBitsSec.["2"])
ect...
ect...

I have about 200 interfaces on this switch and in want to calculate In and Out speeds.