You can manually test your window-level Help by copying the .CHM file into the application folder and then calling Help from each dialog and window. If you test this way, you'll need to manually track the names of the dialogs that do not work properly and then go back and update the aliases in your project.
If you have RoboHELP Office, you can use BugHunter to test your window-level Help. There are two different ways to do this in BugHunter, depending on whether or not you run the application at the same time that you do the testing. It's not necessary to have the application installed on your system to reliably test the aliases. In fact, there are times when the application is not available and you'll need to test the aliases without it. If the application is available, you can display the topics from the application and BugHunter will test their aliases as you go along.
Tip: When you test your topics with the application, remember to test Help menu items and messages.