MySQL-proxy: Setting backend server after checking the SLAVE status

[Mo Dwalkr]

Hello,
here is my problem,
in a Master/SLAVE configuration, I'm trying to use MySQL-Proxy to switch between the Master and the Slave, but not only as a simple failover. Before sending a query from the client, the proxy must check the Slave status (SHOW SLAVE STATUS) and in the case the column Seconds_behind_master isn't zero, the client query must be sent to the Master.
Unfortunately I can't figure out how to do it [sequentially]. The only place i can put the client-Query and my Status-check in the Queue is read_query().
my code structure looks like this:

function read_query()
--append SHOW SLAVE STATUS in the query queue
-- save the client query in a local variable
-- send the query queue to the server
end
function read_query_result(inj)
-- analyse the query result (column seconds_behind_master in particular)
-- set flag
--append the client query in the queue
-- send the queue
end

function connect_server()
-- flag control
-- set Master or Slave UP/DOWN
end

I hope u could understand what my problem is.
Thank you for your help

Regards