This is a common problem.
My usual approach with this is to create property instances with all the possible values for the instance names.
As per your example you create two instances INSTANCE1, INSTANCE2.
The drawback with this is that your compliance rule will only deal with “known” instance names, not simply all of them.
A solution for this would be a script that you run in advance, which browses all the dbs directories, checks for all spfiles and create the corresponding property instances.
Hope this helps
I'm going to create 5 Properties and use a script to populate them IF there 5 instances, or 4 if there are 4 instances and so on..
It sucks regarding style, but I guess it will work
My "ugly" solution is finally working