For a project at work I need to create a spreadsheet for tracking
purposes.  The ideal sheet will provide 2 important pieces of
information:
1.  The total number of items processed by an individual, with a weekly average.
2.  The total items processed by group, with weekly average.
The main concerns are that this needs to be scalable.  Currently Items
are tracked on a daily basis for 4 employees, but there will be a
total of 12 employees.  The goal being to use this information
gathered as an indication of work load balance, weekly and quarterly
performance, etc.

I am an intermediate user of excel, I just lack any design skills.  I
would apppreciate guidance in the best way format the workbook. 
Should I use separate shhets for each employee, etc.