I'm surprised that works, and I don't think it does for most types of loops. The limitation has to do with how looping is handled internally, and removing the limitation is on the todo list.
Other options for now are for one of the loops, to store the results in a macro and use a repeating build rule to iterate.
http://www.kinook.com/VisBuildPro/Ma...scriptloop.htm
Or put the inner loop in another .bld file and call it with the VisBuildPro Project action.
http://www.kinook.com/VisBuildPro/Ma...projaction.htm