I found your 'business hours' solution within this old post and just wanted to thank you for it. My initial testing shows that it should work just fine for my particular needs with a few tweaks to remove the lunch hour and add some alternate time windows & holidays.
You might not have thought that your reply would still be helping folks 6+ years later, but I'm sure glad you saved me a boatload of upfront work on this! Your solution seems much better and elegant than the other solution offered in the thread, since it's set-based.
Again, thanks so much!