Calculation Manager BR and Smartlist - how to reference Smartlist label in FIX statement

Is it possible in PBCS to use in BR in FIX statement a member from Smartlist created from Members?

We need to create BR for allocations. We have created a allocation definition form, where each allocation is defined by 3 smartlist: Source Entity, Source Account, Allocaton Key in Account.

These smartlists members are defined from option “Create From Members”.

How can we use in fix statement for example Source Entity selected in Smartlist?

I tried to use @SmartListFromIndex function in BR scripts

FIX (@SmartListFromIndex("AlokacniStredisko",1))

but compilation is not recognizing this function. I am getting following error message:

A validation error was received from the Planning server.