Like suggested in this post, you can try using queryStatus and filter to get just the specific tag. That will give you a list of alarm events that you can iterate using a script like here and get the IDs.
Your queryStatus call would probably look something like
alarms = system.alarm.queryStatus(status=["ActiveUnacked"], path=[my_tag_path])
where I'm assuming you have your tag path as a binding on the popup already.
EDIT: Like mentioned by @bschroeder, queryStatus is pretty intensive so you don't want to call it directly, use a message handler or invokeAsynchronous