Thanks for the advise. I've given up on this, I can't even get the private message to send - let alone concern myself with checking the usergroup or subscription ID.
If anyone is interested in coding this for me, I've posted a paid work request here:
https://vborg.vbsupport.ru/showthread.php?t=172882
As I posted in the above link, you'll find plenty of code around already to get this job done. I'm willing to pay a premium if someone has the time to get this done today.