Problem with Calculated Items in Discovery rule

[renegade]

I have a problem when I try to create a calculated item in a Discovery rule in zabbix 2.4. I try to calculate the space in bytes of the partitions of a device. For this purpose I use the following operation:

last("sysHostDiskFreeBlocks.[{#SNMPINDEX}]")*last("sysHostDiskBlockSize.[{#SNMPINDEX}]")

sysHostDiskFreeBlocks = Key of item where I get free blocks
sysHostDiskBlockSize = Key of item where I get the size of block in this partition

The error shown in latest data is: Cannot evaluate function "last()": item "itemName:sysHostDiskFreeBlocks.[1]" does not exit.

The same type of formula I used it in a normal calculated item (not a rule discovery) and it works perfectly .

I would be grateful if you could help me solve the problem

[renegade]

I 'll answer myself , at the end I found the problem. The problem was the special values escape and pass to the function last () the value 0:

last("sysHostDiskFreeBlocks.[\"{#SNMPVALUE}\"]", 0)*last("sysHostDiskBlockSize.[\"{#SNMPVALUE}\"]", 0)