Rxclearcông việc

I have a serial device that I communicate with using an activex component. I notice in th test program provided that RXCLEAR and TXCLEAR (buffer flush) are sent before every command but these are not included in the ACTIVEX component. I therefore need a way of flushing the buffers. I have tried using a comport component but this obviously complains that the port is already open when i try to use the flush commands. So i need a way to flush the RX and TX buffers - Simple as that. This is an urgent project.