How do I get MESSAGE value from IQ procedure?

I'm currently calling a procedure from my java application. The procedure contains the following piece of code:

     IF v_throw_exc_flag > 0 THEN      

          MESSAGE 'One or more of the locations exceed the area limit of 10000km2', SQLSTATE, 'SCI.ProcName' to client;

          SIGNAL CUSTOM_EXCEPTION;        

    END IF;

Could someone give me a hint to get the MESSAGE value in my catch(SQLException e) {} piece of code?

I'm currently getting

com.sybase.jdbc4.jdbc.SybSQLException: SQL Anywhere Error -156: Invalid expression near 'CUSTOM_EXCEPTION'

Regards,

Vinícius.