[Serusers] blocking certain extensions

Hi All, I have defined extension 2000 - 8000 on my SIP server. All of them can make calls to PSTN, but my boss wants now, to block all 2XXX extensions to call PSTN but they should still be able to call other extensions from 2000 - 8000. I was thinking of adding something like this line, if ((uri=~"^(sip:)?001[0-9]*@([a-z]+\.)?mydomain\.com") || (uri=~"^(sip:)?001[0-9]*@123\.45\.67\.89")) but the condition will be if calls originated from 2XXX going to pstn, which would look like 00XXXXXXXXX, it's more like this line if (((uri=~"^(sip:)?001[0-9]*@([a-z]+\.)?mydomain\.com") || (uri=~"^(sip:)?001[0-9]*@123\.45\.67\.89")) && (((uri=~"^(sip:)?001[0-9]*@([a-z]+\.)?mydomain\.com") || (uri=~"^(sip:)?001[0-9]*@123\.45\.67\.89"))) but here I compare the destination uri, where should I compare the source? hope you understand my question, as I'm having a hard time explaining in english. Regards Ron