For good or for ill, the answer is simple... no. Dependency relationships are logical ones in Agile Central but they don't get "enforced" in the way that you're describing. A lot of the folks in my company who have the more traditional PMI project management mindset complained about this early on but we've learned that the flexibility of being able to see the dependency relationships but not be forced to honor them in the app has actually been a benefit. Hope that helps.