how to add seq_file based entry under /proc/sys?

Hi,

I'm trying to add an entry with a seq_file type interface under
/proc/sys/net/ipv4.
I just discovered proc_sysctl related changes in 2.6.26 seems to demand a
ctl_table interface on all entries hence disallowing seq_file. Am I missing
something here? Any clue will be much appreciated.

Jerry