I have a spreadsheet that numerous members of teaching staff need to
access to enter data from various places within the school.

It involves clicking on a button to create a new line (line 14) within
a range so that the range expands and can be used in future
calculations.

However I know there will be some staff that will enter their data and
then leave the spreadsheet open hence preventing others from accessing
it.

What I would like is an instruction that could tell Excel to close the
spreadsheet after a certain period of key inactivity.

Alternatively, if I share the spreadsheet and teacher 1 is working on
line 14, what will happen if teacher 2 then clicks the button and
creates a new line 14 and starts entering on it. Will it over-write
teacher 1's entry or will it move teacher 1's entry to line 15 so that
the spreadsheet can be worked on simultaneously by both teachers 1 & 2?

Sorry if this is a bit complicated - please get back to me if you think
you can help but don't understand exactly what I mean.

Many thanks

David