"Negative" font switches

["Giuseppe Bilotta" <oblomov@freemail.it>]

Hello, one more request: I would like to see some font switches that act by
"nullifying" other switches. An example would explain better:

{\bf Some bold {\nobf and some not bold} text}

should be equivalent to

{\bf Some bold} and some not bold {\bf text}

except that the latter would deactivate other possibly existant local
settings. I think this should not be too hard to implemnt ---or is it already
there, and I don't know how to make it work?

Thanks for your attention,

Giuseppe Bilotta