getting result information of DECLARE CURSOR statement

Hi,

I am a new member of this list. I have some problem with postgres CURSOR
(related to libpq).
I have created a CURSOR with :
    PQexec(conn, "DECLARE mycursor CURSOR FOR SELECT * from test");

How I can get how many tuples the result are without I have to fetch all its
result (I use FETCH NEXT instead of FETCH ALL) ?

Thank you for your help

Yusron