asterisk users - Mar 2009 - incoming number information

Dear all. I have next question.
I am using SIP protocol to connect to VoIPGW. Now I need in my
extensions.conf in script to operate with phone number that is passed
to asterisk and insert it into database.
Which parameter is holding A number and can be used in extension
script? Thak you in advance


CELL PHONE ->                GSM OP                      ->VoIP GW
                       -> Asterisk
1234567          -> making call to short number 7777 ->  call is
passing to asterisk    ->  Here i need to operate with 1234567.