Nice Milan,
I've totally forgot about nested repeat region, for me this was no solution.
Hopefully it will do the job for Tomas. Just because of quantities, messing with Repeat Region Relations is not a good idea.
I still stand behind that repeat region is just a dummy, and combining them, or using them to drive anything else isn't really a good idea.
Nesting is fine, but once you get to the point you need to use parameters such as &rpt.rel.userdefined which require Repeat Region Relations, then things get rather cumbersome.