Update the tag database when a single source file is modified

Hi,
Is there a way to ask Global to update its tag database when a source
file is modified? I created a tag database for my project, and when I
change a file in my editor, I'd like to tell Global to update the tag
database only for this file. I don't want Global to rescan the
project, or even the local directory, because I know that this is the
only modified file, so there is no reason to do more work.
If there is no way to do this in Global - can you tell me what type of
database it uses? Can I directly access this database using a library,
and do this update myself?
Thanks,
Shlomy