If anyone could help with this question, I would greatly appreciate it!
Your current workaround sounds pretty good. Unfortunately, my older version of Fireworks (FW8) doesn't have the features you're using, so it's hard for me to advise you.
Here's my suggestion: Would it help to define each nav/menu item in your master page as a symbol? You could drag a second instance onto each individual page to indicate the 'current page'—using effects or transformations to modify its appearance. Then, any changes you'd need to make later on to individual nav items could be made to the symbol, where they'd only need to be made once.
Alternatively, would it be possible to define each nav item as a button symbol (which would include multiple states)? Or to use one symbol—with multiple instances—for all the nav items?
Thanks so much for your help!
Good idea to go with a symbol. Only issue with that, is with my current nav design, when one nav item changes, it affects all the others (spacing / placement). But, still a good approach that saves time! We'll see what happens to Fireworks in CS6...