The Excel Office components won't help because they don't write changes
back to the master workbook (as far as I can tell).
The only tool that will do this for you out of the box appears to be
BadBlue Excel Enterprise:
http://badblue.com/helpxls.htm - it shares
workbooks over the web (end-users only require browsers) and all
updates are made back to the original workbooks. Charts are also
supported.
Check it out and see if it might help.