Query today between time

New to access. I have created a basic query that shows associate's orders completed the from the previous day using " Between Now() And Now()-1" pretty basic. My boss would like to show orders completed between now and the beginning of shift (6:00 AM or 6:00 PM). I'm thinking I need to use the where function but all attempts have been futile up to this point. Any guidance would be appreciated.

Getting closer with this:
Between Now() And (Now()-1+Hour(([Completed Orders test].[Completed Date])>6)+Hour(([Completed Orders test].[Completed Date])<18))

But still not right. Thanks for any help.