I thought I would post a note here because I just went through this.

I was able to just do a same-day change which put me on the 2nd last flight of the day (the last being the redeye) and then out to my final destination on the first flight in the morning, but it seemed like CO Elite desk was willing to let me take any flight I wanted tomorrow.

This definitely has to be done on the phone, the options will not come up online even if you use multiple destinations.