How To Calculate Hours Between 2 or 3 Days Exclude Non Working Hours?

Hi All,

I'm having difficulty to calculate hours between 2 or 3 days exclude non working hours.

Can anyone help? attached is the example of start date with time & end date with time.

The situation is like "when the case log in till the case assist in working hours." so i will get the hours from case log to case assist.

Appreciate expert advice.