Hi Ced,

When opening my "mainfile.xls", I wish it could open others "datafileS.xls",
needed for my calculation within "mainfile.xls". All files are located in
the same
directory.

You can solve this in a number of ways, the easiest being creating a workspace
file.

Open all files that belong together and then choose file, save workspace. This
saves what files you have open at a specific moment. Opening a workspace file
then causes all pertaining workbooks to be opened automatically.

Regards,

Jan Karel Pieterse
Excel MVP
http://www.jkp-ads.com