Use the que functions found on the Advanced -> Synchronization palette...Make a que handler that reads the que elements and writes them to the serial port and reads responses (if any), feed it with new data by inserting elements in the que from wherever you want in the rest of the code...Instead of just inserting the data meant for the serial port into the que you might want to add a header to it that enables the que handler to tag the responses and put it into a searchable buffer...that way the different parts of the application can also get the incoming response if they need to...
You can find general que examples by searching for que in the help->find example window.
