Allowing access to users who are in multiple roles

Hi all,
I have a web.config file with <authorization> section.  I'm using window authentication.
The problem is that I would like to allow access to the web site to those users who are in multiple roles.
 For example:
<authorization>
<allow roles = "Role1 AND Role2"/>
<deny users="*"/>
</authorization>
(Meaning I would like to allow access only to those user who are both in  Role1 AND Role2.)
Is this possible to achive this?
If not, what would be the alternatives?
Note: Currently I'm doing the roles assignment in the Global.asax file in the OnAuthenticateRequest event (i'm reading the groups that the current user belong to in the Active Directory).
 
Thanks in advance,
Mike. 
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