One way (it's a bit rough and ready but it works) is to delete the tag(s) that you want to trace. Then compile the project the compile will fail because of the missing tags and (hopefully) the compile error will indicated where the tgas were referenced. Once you have found what you want to know then undelete the tags. IMPORTANT do NOT pack the databes after deleting the tags as packing will removed the deleted tags from the project completely. If you cannot see any deleted tags in your project you may need to set the "show deleted" option. In Citect project editor got to "tools", "options".
With the new search and replace tool in 6.10 you might be able to achieve what you want by performing a search on the graphic page in question.
another way is to open the pgdynobj.dbf in your project directory, there are all the dynamic objects of every page listed. you could analyse this file to get the info you want. dont try to make project changes in this file because it gets changed automaticly when you save a page, and when you compile your project.
you can also look at the site http://www.ip-powertools.com/ and download the advanced project editor, it has a crossreference module. i have never used it and i dont know with what versions it is compatible.
Version 6.10 has a search tool.
For older versions, I used to use XTree Gold to search this. This program has been withdrawn by the copyright owner, but there may be someone else who has come up with something similar.
I also lost my copy at one stage and could not find another.