Manipulating excel files in Qt?

[Strix Code]

There is a multiplatform (commercial) C/C++ library for reading/writing Excel files called LibXL.
If you can't use that then there is an Java library called Apache POI. You can create a helper Java app using that library and communicate with it from your Qt application.

Edit: @icttrack: You have replied simultaneously with me and now I see that ExcelFormat Library seems to be the best choice indeed.