i head the other day that dreamweaver had a sort of a seek and distroy option. if i needed one change to be made on all html pages that i had dreamweaver had that option to do that. so instead of doing it like 50 time you told dreamweaver where the problem was and how to fix it.
you can do it with find and replace. set it to replace with all the files in a folder, rather then just the file your working on right now.
To avoid having to make the same change in several pages, use Templates, or Server-side iniclude pages. For your queston, Find and Replace will do the job,like Bahamut-Xero pointed out.