Hi Cadence,
I don't have much experience after EPU... But I remember nurse asked me to start crinone 2 days before scheduled ET and also to use at night before bed. I just read in the leaflet that "if you forget a dose of Crinone, use it as soon as you remember, and then continue on the same schedule as before" so I don't think couple of hours would be a problem. Good luck! and good fun at the party!