How can I process the Assign,Evaluate and close the Life Events for around 1500 employees?

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I need to assign a potential Life Event, Evaluate the Life Event and then load the Participant information through HDL and then close the Life Events for around 1500 employees.

The Fast formula doesnt accept more than 100 Employees,so should I create 15 fast formulas?

I saw one suggestion to assign them in Benefit Groups, But I can only Define the Benefit Groups in the Work area, I cannot find a place to assign the Employee Person Numbers to this Benefit Groups.

Please let me know which method would be useful to process these 1500 odd employees?