Here are my thoughts about your approach:

It seems your data is growing to the right as days go by, and your
data grows 'down' as new staff names are added.  I suggest designing
sheets which grow faster downward than sideways.  You have 65536 rows
to work with while only "IV" (or 265) columns.  Grow in the direction
you have the most space.  You'll run out of days after less than a
year if you grow to the right.  That, and it's more natural to scroll
down than to scroll sideways.

Your staff names will then stretch across the top of your sheet, and
days will appear on the left, increasing as you move down.

Second, as I understand it, the staff work in a pattern that repeats
every 40 days?  As a member of your staff, I'll work today if and only
if I worked 40 days ago (and today is not a holiday).  OFFSET() is the
proper function to achieve this.  Staff schedules will all have this
formula:

=OFFSET($A$1,ROW()-41,COLUMN())

...assuming that there is exactly one ROW per day.  This function
pulls the cell value from the cell 40 rows above the current cell.

I would create a Function IsHoliday() which, given a date, returns
TRUE or FALSE.  Then modify the staff schedule formula as below:

=IF(IsHoliday(OFFSET($A$1,ROW()-41,COLUMN())),"H",OFFSET($A
$1,ROW()-41,COLUMN()))

This formula will only produce valid results in or below row 41.
Above that you'll need to define the work pattern for each staff
member by hand.

As the days, weeks, and months go by this technique will create a lot
of cells with a lot of formulas.  It will bog down eventually.  To
keep it fast you should periodically COPY and PasteSpecial (paste
values only) on PAST dates.  Like when you close down November be sure
to replace all the formulas in November with Values.  Values won't
slow down Excel at all.  Don't let your sheet fill with thousands of
formulas calculating historical dates...

Hope this helps a little.

Brian Herbert Withun