Please help;

I have an excel timesheet template covering the activities of a group of
people.
The activity names and personnel names in the table do not change.
A new file is created each week and the filename is the Friday and the Month
i.e. 1512.xls (15th of December)
I want a new workbook to provide totals of time entered against each
person/activity(as hours) in each file.
I want the file to be live so that it updates as new timesheet files are
created.

I would envisage it as being the same layout as the weekly timesheet, only
it would show overall totals. I don't know how to bring in these totals from
the external workbooks, or how to keep it 'live' as new files are added.

Thanks
D Dawson
Scotland