I currently have a workbook of around 25 worksheets, with 1 summary
worksheet. The 25 worksheets are of identical format but have
different names (sorted alphabetically).

On the summary page I have used functions such as SUM(BBB:YYY!$B$1) to
get total values. However I am currently adding 3-4 extra worksheets a
month and I would like these to be automatically calculated in the
formula (i.e. if I add sheet AAA or ZZZ, I will have to manually adjust
the formula).

Is there a formula that shows the name of the first and last worksheets
so that I can add an INDIRECT command to my formula and have it
automatically update whenever I add a sheet? Or is there another way
of approaching this? Ideally I'd like to avoid using a macro as this
will be sent out to dozens of people, many of whom probably have their
security settings on high.

Thanks,
BH