[Asterisk-Users] astersik sip routing question

[m. smadi]

hi;

i am trying to perform some routing logic based on the recieved SIP 
requests.  In the past i have used Sip Express Router and in ser.cfg you 
can for example perfome operation on the a request or parameter before 
continunig to route it.

1 - Now is there a way of doing this with asterisk? 
2 - Could this be related in someway to writing SIP-CGI or CPL scripts? 
can i invoke a given script based on the reciepts of a given request for 
example?

thanks
m. smadi