Virtual Serial Port

I want to create a Driver Which will create two virtual serial ports COMx,COMy but It has to use Only one serial port on the system say COM1. The necessary switching will be done in the driver(Queing all reads & writes from one app while other app is using the Port). I am new to this driver programming.

Can anyone give me some sample or sugession to proceed with development.

Is it mossible to do this in user mode?

--chandu