Use an item to pass multi-select prompt in ES

[ricky_ru]

Dears,

I have a report with a multi-selec prompt. The filter is like [product_line_code] in (?plc?).

I create a Event Studio, add this report as a task.  For the plc prompt, I can use the method [use an item] to provide the prompt values.
I want to create an item in the insertable objects panel , providing some constants to define the item then use it for the prompt values.

How to define it? See image attached.

Thanks,
Ricky