[texhax] Hacking the log file

[Vittorio De Martino]

I use pdflatex in a production context with the  textmerge package to write  
letters to some 1800-2000 firms twice a year; in between I write - always 
with textmerge - far less letters (200-300 to urge people not responding to 
the bulks sending to reply) four times a year. 
If something goes wrong while running pdflatex, I can find the error but it 
requires some tedious work and checks. 
What I would like to do with while running pdflatex to merge letters is to 
write into the log file an extra information like, for instance, the name of 
the firm which, of course happens to be one of variables of textmerge 
(\Firm).
What should I do?
Vittorio