evaluate rendered text lenght

Hi all, I would like to evalutate the lenght of a string as it will be
rendered in FOP. Of course, because of FOP formatting strategy, this
info can be just an approximation, but for my purpouse can be enough.

I've seen the Eliot Kimber extension (Function "renderedTextLength")
but it is no longer available on Innodata Isogen web site. There are
other alternatives?

TIA

Giuseppe Briotti