How can I wait on Windows-systems without consuming CPU?

You might want to try "sleep" command. You can put the command into a .bat file and execute it from Appx with /w. Here is link for a free download of a resource kit tool for Windows 2003 that contains sleep.exe command: http://www.microsoft.com/downloads/details.aspx?FamilyID=9d467a69-57ff-4ae7-96ee-b18c4790cffd&displaylang=en

Or you can take an approach as outlined there:

https://www.appx.com/assets/asp/dynamic_generator.asp?pageid=161