I get it would be difficult to have to see him everyday. Try making a challenge out of it:
You said you have to figure out the schedule each day with him. Can you email it to him, asking for input?
Keep every interaction as business and short as possible. Challenge yourself to speak as little as possible when you have to talk to him. Think of him as an acquaintance you don't really like but have to get through the discussion with. If it took 30 words today, see if you can down it to 28 tomorrow.
I don't know what your job is, but if you aren't interacting with the public or answering the phone constantly, can you put earphones on, and ignore him going by? Just concentrate on what you are working on?
If he stops by and wants to talk about the old days, or about possibly coming back, just say, "Sorry, I can't discuss that right now. I have work to finish." Then turn away and get back to work until he walks away.
Just find ways to interact as little as possible, and keep it TOTALLY business. Don't let him suck you in. It will get easier.
I'll give you a funny, if it might help. My XH and I both officiate a sport. The first time after Dday that we ended up at the first tournament, there was an elite level playing. The two of us were part of the crew of 4 the boss wanted doing this level. When we were discussing who would be working with who, my STBXH insisted to the boss that he would love to work with me. Boss looked at me, I said, whatever.
The players were confused as they knew we were Sep. Had a few questions there. I just kept reminding them they were so special, I was sucking it up for them.
In between two games, my STBXH sat there, rubbing his chest. I looked at him and asked what was wrong. He said he was having pains, thought maybe he was having a heart attack. I looked at him for about 10 seconds and told him to get up. What?!? he said? I said, Get up. If you died right now, NO ONE will believe I didn't do it. So get up and get your ass back out there. You can have your heart attack when you go home.
A couple of players heard this exchange. They laughed their way through the next game. BS(me) 46, Two wonderful teens.
He is no longer my best friend. Repeat until it sticks.
WH says marriage is over: May 15, 2009.
EA#2 July 20, 2009. Legally sep: Aug 16, 2009. DIVORCED!!!! Signed Nov 23, final Dec 24, 2010, adultery listed.