asterisk users - May 2009 - Numeric Hangup Code

I am sending SIP or H323 calls to a carrier, and I need to store in the CDR
why the calls are rejected or why they hang up. In SIP, it can be code 503,
500, 488, etc. How do I get the information in my dialplan? I don't mean
$(DIALSTATUS}, but the real numeric code 
F.Alves