You can build some awesome progress indicators utilizing the FileMaker web viewer. Because they do not require a plug-in they display well on FileMaker Go as well. They also do not require access to the internet because the html for the web viewer is embedded directly in FileMaker.
These examples are very simple to display from script control by changing the value of the global variables $$progress or $$progressText. If they are blank, nothing will be displayed.
See the updated version of this sample file here.