Word count of track changes

Hi all,
Here's what I've been struggling with today.
I have a marked up amended document (50 pages or so) with almost 600 changes (additions and deletions). Is there any way I can do a word count of the amended text only in MS Word?

Some text has been deleted, some added and some amended. I need to get an estimate of how many words are underlined in the marked up version of the text, so that I can tell the client what the cost would be.

Any help will be greatly appreciated.

THanks!