Statement Triggers. Ideas & help.

I´m trying to implement Statement Triggers in postgreSQL. The basic idea is
check (in ExcutePlan) if there are statement before call first time to
ExecAppend, ExecDelete or ExecUpdate (or after the last call in case of
after statement).

But if I exec "Insert into tbtest values (22,'cadena');" then ExecutePlan is
call two times, and ExecX too. Why?
The execution trace is:
Entering ExecutePlan
Calling ExecAppend
Entering ExecAppend
Entering ExecutePlan
Calling ExecAppend
Entering ExecAppend

Other Question: SQL3 says
" The execution of triggered actionsdepends on the cursosr mode of the
current SQ-transaction. If the cursor mode is set to cascade off, then the
execution of the <triggered SQL statement>s is effectively deferred until
enacted implicitly by execution of a <commit statement> or a <close
statement>. Otherwise, the <triggered SQl statement>s are effectively
executed ..."

How apply this to postgre?

Thanks everybody.

F.J.Cuberos