dblink_exists

Hello,

I need a function like "dblink_exists()", but there is no one.
Here is my script:

create function trading.stats_symbols()  returns boolean as  
$$
declare
sql text;
begin 
sql='...';
truncate trading.stats_symbols ; 
perform dblink_connect('updatesymbols', 'dbname=ftc') ;
perform dblink_send_query('updatesymbols', sql) ;
perform dblink_disconnect('updatesymbols') ;
end;
$$ language plpgsql;

My general problem:
I need a command that send a answer immediately and not, when the query
if finished.  
dblink_send_query connect with the own database and runs a long time. 

When someone start the script again (when it is running), so I need a
section like:

if dblink_exists(updatesymbols)   -- but this function do not exists
then 
return false -- or do nothing
end if;

dblink_is_busy is not usable: when the function is not running, it
stops. 


2. question:
When dlink_send_query is running, 
select dblink_get_connections() 
send NULL as answer. 


Franz