Find
Try this trick:
Close the RSView application.
Under START, select Find... | Files or Folders
Search for a file neames *.*, containing the text of your tag name, looking in the folder where your RSView application is located.
This will give you a list of all the screens that use the tag (*.gfx), all the parameter files (*.par), macros (*.mcr), event files (*.eds), and whether it's used in VBA somewhere (project.vba) (as well as the tag database ?(project.db - but the VBA and tag database don't show up if the project is open - go figure).
Fortunately, even though the files themselves are compiled, the tags are stored in plain ASCII, and so Window's search engine can find it. This won't tell you WHERE or HOW it is used, just that it is. But it shouldn't be hard to do a search within the object (except for screens, but then you've got the documentation utiltiy for that).