Week to date figures calculated on external spreadsheet?

[ugg]

Picture this:

Daily Spreadsheets all with the same naming convention
Example
January 1 2008
January 2 2008
January 3 2008 etc

Is there a way to have a weekly spreadsheet that references the same cell in each to give a week to date total?

Secondly and more difficult, is there a way of only having it look at the last weeks figures so that it is easily maintainable with minimal effort?

Any solution anyone can offer would be great

[royUK]

Take a look at the summary example here

http://www.excel-it.com/workbook_downloads.htm

The best way though is to have all data in one sheet & group it by weeks, see

http://www.excel-it.com/pivot_tables.htm