[TYPO3] Negate access to content elements by a FE usergroup

[Claudio Strizzolo]

Hi all,
I have a page which can be accessed only by logged-on FE users.
I need some content elements in the page to be readable only by users 
which DO NOT belong to a certain FE usergroup (let's call it "badguys"), 
while other elements must be readable by any FE user.
I know how to allow access by an usergroup, in the "General options" 
section of the content element in the BE, but do not know if there is a 
way to reverse such a permission ("allow everyone except badguys").
I would not like to define a second usergroup including all the users who 
do not belong to "badguys".
Any hints?
Thanks in advance

Claudio