TsuFilesInUse
The installer sets this variable if it encounters an in-use file that must be replaced. In that case, a reboot is required to complete the installation.
Usage
Used internally by the installers. You can refer to this variable as <TsuFilesInUse>. In conditional expressions you can omit the brackets and simply use TsuFilesInUse as a test for delayed file copying. Set automatically by all installers.