I have an odd need to open two separate instances of excel and having each open a different spreadsheet for various manipulations.
At the moment I'm doing the simple execution of excel with command line parameters to open the two spreadsheets, but both spreadsheets end up in one instance of excel.
Yes, it's klunky, no, I can't easily explain my reasoning for this odd requirement.
Hopefully, however, you have a few suggestions I can try.
You didn't say what language you were using, but look at these links. For perl http://www.xav.com/perl/faq/Windows/ActivePerl-Winfaq12.htm for vb.net look at http://support.microsoft.com/kb/302094
If you're not trying to programmatically access each instance of Excel, you can set Windows Explorer to open each workbook in a new instance:
http://www.vadriano.com/excel-vb/2007/04/12/how-to-open-excel-files-in-a-new-application-instance/
In your command line call are you specifying the full program path for Excel? When I do that from the command line I get each file in its own instance...
As far as I can tell though, you can't open/control two separate instances of Excel programmatically at the same time...