you would have to have an IR receiver card added to the PC that wakes up with IR commands.

it would be a good idea for you to download the MX450 archiver software and make a backup of the configuration before trying to edit it.  this way if you mess up, you can go back to how the original installer programmed it.

here is the software
[Link: universalremote.com]


and here is a link to the manual that gives you basic programming steps
[Link: universalremote.com]