create a table of dates/times based on weekly shift start and finish times and holidays

i'm trying to make a list of dates and times based on a table of days of the week and shift start time /stop time also holidays

if day is blank then no work on that day
all times can vary

This is a bit clunky and works OK for what i need to do
BUT
it would be useful if i could change any time and the list expand to include those time

Column I is the table of dates and times - each minute
row 2 = now()
row 3 = sets now to a minute with no seconds
row 4 (I4) is where the formula starts
looking at the previous day and time compares with the shift table to see if its a saturday or sunday and IF there are any start stop times it inlcludes those shifts
if not it goes to Monday and looks at the start time and uses that
otherwise it just works Monday to Friday 24 hours

just would be useful to put any of the shift times in and have the list generate

also if its a bankholiday / holidays- look at the next shift and see if that is valid and use that - otherwise move on to the next day and check that
I have a list of holidays

I only need the table of minutes to run for a month - so 50,000 rows - this example just has 2000 rows to show a day and the change over , to keep the file small for the forum
Just drag down to extend

any suggestions