[Serusers] how to add a header into the reply??

I want to add some extra header to the positive responce. I don't want to attain that in script, instead I want to do that in the code or another module. What I did is to add the following into the reply_received function. if((t->flags & T_IS_INVITE_FLAG) && (!is_local(t)) && (msg_status >=200 && msg_status <300)) { typedef int(*local_fp)(struct sip_msg *msg, char *txt, int flags); local_fp append_to_reply = NULL; append_to_reply = (local_fp)find_export("append_to_reply", 1, 0); if(append_to_reply){ DBG("DEBUG: SUNZJ find apppend_to_reply\n"); append_to_reply(p_msg, "P-Security-Nobody: this is a test header for \r\n", 0); } } But it doesn't seem to work for me. I can't see the added text from my SIP UA log. How could I get to that?? Thanks for your instructions! Best Regards Sun Zongjun