Inter Layer Checks - Same Subclass to Subclass?

I'm trying to define a set of "Inter Layer" checks that I can use for our flex and rigid flex designs and noticed that I cannot set up a check for items that are on the same subclass.  Maybe that is not the intention of these checks, but it seems like it would a little more useful if you could do this.  As an example, I'm trying to define a check that would ensure two stiffeners, added to a flex circuit on the same side, are not too close to each other.

Is anyone aware of a way to automate this check using the Inter Layer table of checks?  Maybe another way?

Thanks in advance,

Scott