The easy way out is to save (export) the Excel sheet to a txt file. Then read and parse the txt file.
If you really want to import Excel files, you need to use ActiveX. And that has consequences... Any executable you'll build will be hard wired to the exact Excel ActiveX version. So it will be a disaster if you distribute to more then one or two systems (or if IT updates Excel on those systems). That is an old problem, but I don't think it has been solved. Hopefully, but doubtfully.
You'd probably be better of looking for a .NET Excel\Office library.