Can't load Excel Interop c#

He Guys!

Im trying to load the Excel Assembly. As reference I use Excel.exe. But when I open the Editor there is an Error message "Import failed for 'C:\Program Files (x86)\Microsoft Office\Office14\EXCEL.EXE': The File or Assembly "file:///C:\Program Files (x86)\Microsoft Office\Office14\EXCEL.EXE" was not found. An assembly manifest was expected.

Does anybody know a solution to that problem?

Thanks

Lukas