reading messages over serial port

I have a matlab executable program running on a PC, where at the same time an application is running which monitors a UPS device feeding the PC. The communication between this app and the UPS device happens over a serial port. I wish to monitor this communication from within my matlab program to find out when battery mode is activated, so as to shut down all operations on the PC as well as the PC decently in that case. Since the port is already in use, it is not possible to open and configure it in the matlab program. How can I monitor nevertheless the communication?

I did download a separate tool which is capable of doing this. This allowed me to reverse engineer the messages and determine how the battery operation mode is signalled. Question now is how to do this in matlab? If possible of course. Anyone has done this before?

[Walter Roberson]

There just might be a way to use a .NET Assembly to do this, maybe. Not that I could name one at the moment.

I see that https://sourceforge.net/projects/realterm/ mentions having an ActiveX/COM interface for monitoring.