Is there any easy way to refer to sheets without knowing the name of the sheet?

e.g. A summary sheet that collates details for the company from all other
sheets within the workbook which may be different branches and/or personnel.

These extra tabs may be added or have their tab name changed at any time,
and I do not wish to redo the summary sheet each time.
Ideally I would like to know how many other sheets there are are and to be
able to reference instead of 'Freds Sheet'!.$A$7 to be something like
WorkSheet[3]!.$A$7, with some method of checking the range of sheets - the
summary could always be the first sheet.

The sheets, other than the summary, would all be in the same format, so that
the data required would be accessed from 'fixed' cells.

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Eric Hargreaves