Additional arguments to a module

[Daniel Ivanov]

I want to add an additional argument to the ipt_MARK.c module.
Where do i register that one? I would like a check for true/false(0/1) 
on that argument and different return code accordint to the value.
like :
iptables -t mangle -A PREROUTING -j MARK --set-mark 5 --my 1
 to be acceptable.
I suppose it has to do with targinfo , but don't know how to act 
further. Any clues appreciated.