If there is no sheet with the same name in the second file, nothing happens. It seems to me as a really boring bug. Anyone else with the same problem? Any idea how to solve it? (Excel for Mac 16.21 (190108), but the problem also happened in previous versions). To get the latest update, open Excel for Mac, go to the Help > Check for Updates menu, and follow the instructions in the AutoUpdate app. For the most recent information on this issue, go to Problem opening files or folders via hyperlinks in Excel 2016 for Mac.
I can teach myself Objective C on the web and set 'write Excel viewer' as my first assignment. As already stated in other answers, you can use Apple's 'Numbers' to open Excel files, but creating or modifying Excel files programatically is a different story; you might need to have the appropriate tools (SDKs etc.) installed to do that. May I ask what tutorial you're following? If the guide has prerequisites, it should specify how to meet them. (Depending on what exactly you want to accomplish, this might actually be a question better asked on StackOverflow).