[plt-scheme] Profiling

I have a question about using the profiling tools in errortrace.ss. My 
program is essentially a pipeline of procedures that manipulate a 
reasonably large datastructure.

I'd like to profile only one of these procedures; my thought was to 
insert a "dummy" procedure before and after the procedure I wanted to 
profile; the first would looks like

(define start-profiling
   (lambda (h)
     (profiling-enabled #t)
     (profiling-record-enabled #t)
     (profile-paths-enabled #t)
     h))

followed by the target procedure, followed by

(define end-profiling
   (lambda (h)
     (profiling-enabled #f)
     (profiling-record-enabled #f)
     (profile-paths-enabled #f)
     h))

Now, for a variety of reasons, I've decided that this doesn't work 
(mostly because it didn't work).  I can get profiling information for 
the entire program, but that's a bit much; it would be nice to collect 
profiling information on the one procedure only.

Is what I'm looking to do possible, or should I just take the profiling 
records and try and filter them based on source information in the 
syntax object?

Thanks,
Matt