Some legacy software relies on downloading multiple Excel files, merging the contents, sending it back out, someone far away making some changes to it, and then sending the modified Excel file back, where the next day the multiple Excel files will be downloaded again and merged with this file. Is there some tool (preferably for Java or that can be used from a Java program) that would allow me to replace this legacy code, as maintaining/extending it is only slightly preferable to self immolation?
I should add that the reason we're using Excel at all rather than a database is that some of the reports can only be exported as Excel, and on our end some of the staff are comfortable with using Excel formulas. So we would need something that they can edit in an Excel like way but that we can do all the above to otherwise.
Update: These files contain no images, just normal Excel data and formulas. I'm leaving "sending" generic because that can be changed pretty easily. It could be by FTP, by email, by web form, etc., doesn't really change the nature of the process.
If you're looking for a library for reading and writing excel files, take a look at http://jexcelapi.sourceforge.net/