Call to build-in operator from new operator

Greetings,

I don't really know if this is the correct place to ask this question, if
not please direct me to the correct mailing list.

I'm trying to develop a new operator for PostGreSQL (actually for
TelegraphCQ, which is an extension of PSQL). Part of the operator's
procedure is the @-operator. So now my question is: How do I call the on_pb
function from inside my own function?.
The on_pb of course takes the argument 'PG_FUNCTION_ARGS' which is defined
in fmgr.h as 'FunctionCallInfo fcinfo' which is defined as pointer to
'struct FunctionCallInfoData', so my question boils down to:

What do I put into this struct to call 'on_pb' with two arguments from the
call to my function?

Further, is there a way to access data in tables in the database other than
those given as arguments to the function? And how?

Sincerely
Kim Bille
Department of Computer Science
Aalborg University
Denmark

--
"Mind are like parachutes --- they only work when open"