[Freeswitch-users] Is there a group variable?

Hello! I have the following scenario: I want to check if a called extension is part of a group, or as an alternative, if it is a user in the directory. My basic intention is to find out if a 3-digit extension leads to a valid user - if it doesn't, some other action will happen. Maybe there are better ways to do this than to check for the parameters above, not sure though(Don't want to use a regexp for the available extensions though). If there is such a variable, it doesn't seem to be documented or i'm still too lost in the docs... Can you give me a pointer? Regards Christian