How do I represent this counter with period in BPMN?

Dear all,

I'm modeling a process where there is a task of the Multi Instance Loop Type, called “Accounting records”. In this task, I cannot define in Basic Properties, number of Star Quantity , because the value depends on the number of records made in a certain period.

Before, I would need to have a task that counts the amount of registration for a certain period. This counter will set the Start Quantity value of the Multi-Instance Loop Type. How do I represent this counter with period in BPMN?

Best regards

Felicio