Hey, Einar,
If you ever find a good answer on that one, let me know. I've tried to figure that one out as well.
There's an option to "reimport" a subreport in the CR designer, which leads me to suspect that it doesn't automatically work the way we'd like it.
Maybe there's a way to programatically reimport at runtime, though the object model, but I've never looked. Maybe I should give it a try.
Kevin