sendsms?customparam=....

Hi List,
It's me again, after days of looking kannel source code. I'm interested
on how to add a custom sendsms parameter. Currently I have successfully
added a custom parameter item in msg-decl.h:
MSG(sms,
	{
...
INTEGER(customparam);
...
}
And try to add it into smsc_http.c:
...
if(sms->sms.customparam == 0 && octstr_len(sms->sms.customparam)) {
        	octstr_format_append(url, "&sms=%E&smstype=0",
sms->sms.msgdata);
      }
...
The compilation was succeed with no error. But when I try
to do http://host/cgi-bin/sendsms?customparam=.. and checked the log.
Kannel still can't grab the customparam value. I think, I miss some
other things to be patched here. Still looking around but no clue. So
can you help to figure it out? Many thanks for your kind help and
assistance.

Regards,


Willy