'Automatically' may be a bit of a stretch. You are going to have to select the text you 'tag' before you can tag it (or the paragraph containing it), and then you are going to have to run the macro to process the information. However, how do you plan to tag the text. What do you mean by 'tag' in this context.
You could perhaps bookmark the text then insert a cross reference to the bookmark.
http://www.gmayor.com/BookmarkandVariableEditor.htm will display all the bookmarks in the document, with their values, and will create cross references. That may help, but until you define what you mean by 'tag' in this context, that's as good as it gets.