page xy coordinates for musical events

[Nicola Montecchio]

Hello

I'd like to know if there is a way to get the resulting coordinates (i.e. x/y
position in cm on the page) of a musical event in the compiled ps/pdf file; what
I want to do is to typeset a lilypond source, and LATER post-process the
resulting image. The typical case would be for example highlighting a specific
bar. Note that I do not want to do that directly in lilypond, but as a
completely separate step.
I tried looking at the documentation, but could not find anything.
Any hint?

Thanks in advance
Nicola Montecchio

-- 
Ing. Nicola Montecchio
Ph.D. Student
Information Management Systems Research Group
Department of Information Engineering
University of Padova, Italy
Phone: 0039 049 8277929
http://www.dei.unipd.it/~montecc2