I didn't figure it out; my previous answer, as you may have found, is wrong. I found this on another forum, posted by Macropod:

Press Ctrl+F9 (the F9 key, that is) twice, which inserts a blank field containing another blank field. After the first curly bracket and space, you'll insert an equal sign. Then the next curly bracket will follow with its space, then type NUMWORDS. The existing space and bracket follow. Then type the number of words on your title page (counting them as I suggested above), which will be followed by the existing space and final curly bracket, like this:

{ ={ NUMWORDS }-4 }

Thanks, Macropod! After realizing that my solution didn't work, no matter how I arranged the -#, and spending nearly an hour trying to find it clearly presented in Help or on the web, I found your reply.