There was a thread on here not too long ago about this, and a link popped up to the Siemens tech support pages, where they had a FB for the Siemens PLC and an AOI for the control Logix PLC that allowed them to communicate directly over ethernet with no middle man. They had instructions and examples for implementation, the whole works.
However, if you have a little more money to spend, I'd be looking at a Red Lion Data Station Plus, or a Prosoft module like this one. It'll save you a lot of headaches.