Shared workbooks

[Scruffymessiah]

Here's the project that I am attempting... I have compilesd a workbook that summarises an employee's weekly timesheet, this then gets posted to the finance department for processing. The summary has been departmentalised and it is up to the several Head of Departments to input the information. I have asked them to save the file under a different name (eg department name then date) with each use. How can I create a quarterly (or yearly) summary sheet when the saved name changes every week. We would prefer for this system to run without a dedicated supervisor. Can anyone help?