Hmm... does it come with a ASIO driver, or is it one of the Behringer interfaces which only work with ASIO4ALL? If the latter, then you know what your problem is.
Edit: Yep, just checked. ASIO4ALL. Well, I don't think ASIO4ALL can do what you're asking for.
And, TBH, it's absolutely ridiculous that Behringer doesn't provide their own ASIO driver for their audio interfaces. ASIO4ALL is a workaround solution when there's no specific ASIO driver available for your general use sound card, not as something you'd run for your dedicated audio interface.