Sum or aggregate interface

In attachment file in zabbix i create with the discovery the item with key 

aggregate.in.cos.[762]

aggregate.in.cos.[916]

aggregate.in.cos.[703]

i wold like create a item with the sum of this item for create a custom graph.

grpsum["Mikrotik core","aggregate.in.cos[*]","last","0"]

if i use this key the sum not work why the key aggregate.in.cos[*] not exist.

the [*]option not work for select all item 

• There is a special command for select all item 
• There is another way to sum the iteem

Thanks for help