Hello
I would like to use excel to make a rosta easier to manage. Layout
would be roughly:

Time......... 9am 10am 11am etc
Group 1.... maths english drama
Group 2.... english drama maths
Group 3.... english maths drama
etc

So my question is, how would I go about limiting what can be entered
in each cell? If the rule was that maths can only take place by one
group at any given time. Also, if english can only be taken by two
groups at any given time. And english cannot be taken at 11am by any
of the groups?

So I wish to start with a blank canvas, but when I start entering
class values (english, maths, etc) then this limits what can be
entered in other cells. Preferably a drop down would display all
possible values for any given cell, based on what has already been
selected in other cells.

Many thanks in advance for any advice.
Regards