How to calculate working hours spent for a CASE on a activity

For Ex Time spent on Deliver block activity. I am using below formula

DATEDIFF ( HH, PU_FIRST(VBAP, “_CEL_O2C_ACTIVITIES”.“EVENTTIME”, “_CEL_O2C_ACTIVITIES”.“ACTIVITY_EN” IN (‘Set Delivery Block’, ‘Set Default Delivery Block’)),
But this formula will consider weekend and holiday hours as well.
Please let me know how to get the working hours only .

I have tried below formula as well after looking at

as i dont have any calender table to use.But Below formula is also not working.

CALC_THROUGHPUT(FIRST_OCCURRENCE[‘Set Delivery Block’] TO LAST_OCCURRENCE[‘Remove Delivery Block’], REMAP_TIMESTAMPS("_CEL_O2C_ACTIVITIES".“EVENTTIME”, MONDAY 08:00-17:00 TUESDAY 08:00-17:00 WEDNESDAY 08:00-17:00 THURSDAY 08:00-17:00 FRIDAY 08:00-17:00 ),
REMAP_VALUES("_CEL_O2C_ACTIVITIES".“ACTIVITY_EN”, [‘Set Default Delivery Block’, ‘Set Delivery Block’])