Serial ports two different applications on one computer monitoring activity on one serial port

Question

I have an application writting to a display unit on a serial port.
I have been asked to write a VB net 2005  application, to also run on the same PC at the same time, and monitor the activity on that port being used by the other application. I have to convert the serial ouitput from the first application and then write it to a secondary monitor.
I just cannot work out how to read the serial port from the second application whilst the first application is active. I cannot open the port as it is being used by another application.
Am I being asked to try the impossible. I believe not as Port monitors seem to be able to do this.
If anyone could help I would appreciate it.