Just an idea but you could insert like 6 empty basic scripts at the end of your program, not really a custom sound but it would be a BEEP BEEP BEEP BEEP BEEP!
Attached are 2 files, CMM_PlayFile.bat and CMM_PlayAudio.bat (as .txt files to upload to the forum).
Change their extensions and place them in the same folder. Have some code in your PC-DMIS program to run an external program ponting to the batch file. I can't remember if you have to set it to a loop or not.
Have a file name CMM_Alarm.wav in the same folder and it will run it. (I have one but I can't upload it for 20kb limit)
Can this method be used to play a specific video file? Does the media program need to be specified or can it only use the windows default for that media type?