Thanks Bob

I just referenced the relevant cells in the same sheet, Named Range
are a neat trick

One issue, what I am trying to do is give a visual of the 24 Hours in
a day and for each hour show whether the premises is open or not. Thus
in my example above a check for the hour of 7:00am, would be if this
hour is between the stated Open and closing, change the colour of
7:00am cell to "Blue". But what if trading hours straddle 2 days i.e.
Open = 6:30am and closing is next day at 2:00am?

Based on the formula above 7:00am would not be between 6:30am and
2:30am

Any ideas?