A successful split:

I was able to use Expedia.com's multiple cities reservation to ticket me ORD-MEX-SJO-MEX-ORD even though ORD-MEX and MEX-SJO have the same flight number (as do SJO-MEX and MEX-ORD for the return flight). The fare was a bit higher ($30 or so, incl. $5 to Expedia) than booking directly through ual.com as ORD-SJO-ORD. I am keeping my fingers crossed, as I haven't flown yet, but I did get Expedia to confirm that I would receive miles for both segments (not that UA will care what Expedia says).

I had been frustrated quite a bit and unable to do this on travelocity and orbitz (except at much higher prices), ual.com, 2P reservations, or mileage plus. It's about 1300 miles difference over the whole trip, and in this case it actually means the difference between 1P and 2P for 2004 so I am glad I persisted.

I do wonder what will happen when I try for an upgrade. Will they let me upgrade the whole itinerary for two awards, or will I have to upgrade each flight individually? Well, time to find out.

Anyway, you may want to check the non-UA travel sites to see if they will issue tickets this way. As I say though, I am going to be pretty vigilent until I actually get the miles in my account.

Art