highlighting a scheduled time for tennis booking by using a start time + 90 min

highlighting a scheduled time for tennis booking by using a start time +
90 min

I'll qualify the following by emphatically stating that I'm a rookie. I'm
a manager at a tennis pro-shop and I'm trying to design a scheduling
system. So far, I've made good progress, but I have to be concerned with
my staff that are a bit older and don't need to be relied upon for
multiple "clicks" in order to book courts.
So, I have a column A that has "Start Time" using a validity list in 10
minute increments of my day. It also has a choice of "Lesson/Clinic" and
"Open".
In column B, I'm able to use:
=IF(F18="OPEN","OPEN",IF(F18="Lesson/Clinic","BOOKED",IF(F18+90/(24*60))))
So, column B will show the next available time. If it's a "Lesson/Clinic"
it shows "BOOKED", otherwise it adds 90 minutes to the start time to show
the members when they can bump someone b/c their time is up.
MY WISH/PROBLEM is that I would also like to capture this data going
forward so that I can predict maintenance schedules, plan tournaments and
clinics in downtime, and have a better visual for the members to see along
a daily timeline that's stretched out to the right in 10 minute
increments.
SO, can anyone tell me how to, using the data generated in column B for it
to "highlight" that respective 90 minute window out to the right?
Any help is greatly appreciated.
Best Regards,
Chris