How to support foursquare at special events

foursquare

I've been trying to figure out how to add locations for special events (conventions, tradeshows, etc). So far no luck. What's the procedure for doing so? Some of these events I can visit beforehand if a GPS check-in is required, but many of them I'm unable to visit (as we may be sending sales people to an event a thousand miles away from where I am).