I realise this is an old thread now, but I am doing something similar, but instead of availability during working hours, I am looking to do non working hours.
Our non working hours are Mon-Fri 18:00:01 to 07:59:59 (the next day), BUT I also need to include Sat and Sun as these are also non working hours. I've been bashing my head for hours trying to come up with the right combination of filter conditions, but nothing seems to get quite what I want. So that's why I thought I'd ask here
Hope someone can help
Regards
Adrian