I've had a couple beers, so sorry if the following makes little sense.
You should be able to access each Excel spreadsheet via the Excel COM API using powershell, vbs or any other windows based scrpting language - there is quite a lot of documentation out there - but you need to make sure the machine accessing the excel documents has Excel installed.
Have a search on google for vbs and excel and you should find plenty of examples:
Justkez.com » VBScript and Excel
Microsoft Excel VBScript Script samples
Drop me a PM if you need any help.
Rich.