What is the easiest way to control the DTR or RTS lines on a serial port on a windows system with XP Professional?

I am programming C++/MFC using Visual C++ 6.0. I am connecting to a Pololu servo motor controller and my serial (RS-232) commands are working fine. I am using a simple serial communications class called “Sio,” but the Sio class is limited. I am also using the include files, <windows.h> and <mmsystem.h> and coding information found at http://msdn2.microsoft.com/en-us/library/ms709377.aspx to connect to a USB joystick. I would like to control the DTR or RTS lines on the serial port, so I can reset the controller via software control by causing one of these lines to go low, and then back high, for a few milliseconds. What is the easiest way to control the DTR or RTS lines on a serial port on a windows system with XP Professional? Thank you for your time.