Monday Hour One Follow Through

I’m starting Monday Hour One (MHO) this week and believe I am overthinking it. I know we plan the whole week during MHO and we shouldn’t change it because then we are going back on our word to ourselves. This week, though, I need to make an appointment but have no idea when there will be availability. If I knew, I would schedule that time. What if the appointment ends up interrupting something I’ve already scheduled, like my focus time? Is it okay to switch things around after MHO for situations like this?