How can I get the data acquired via this expression?

[ZaBlitz]

I'm trying to monitor the average value acquired from this expression (avg(/Huawei VRP by SNMP/net.if.in[ifHCInOctets.{#SNMPINDEX}],15m) so I can display it in Grafana, but when I try to create a calculated item, it provides me with this error:

• Cannot evaluate function: item "/Huawei VRP by SNMP/net.if.in[ifHCInOctets.{#SNMPINDEX}]" does not exist at "avg(/Huawei VRP by SNMP/net.if.in[ifHCInOctets.{#SNMPINDEX}],15m)".

What am I doing wrong exactly? I'm kind of a noob when it comes to Zabbix so it's possible that the solution might be so much simpler than what I'm making it out to be...

[troffasky]

Are you creating an item or an item prototype? {#SNMPINDEX} will only be valid for LLD prototype items.
If you are new to all this, I would suggest creating it just as a normal item first and once you are happy that the item represents the data you're after, then look into creating item prototypes - the feedback loop will be shorter.