申し訳ございませんが、本日は満席となっております。
I'm sorry, but I have a previous appointment for tomorrow.
Unfortunately, I don't have time today.
Thank you for today despite your busyness.
I appreciate your cooperation today.
Unfortunately, I don't have time today.
Thank you very much for making time for me today when you're busy.
Thank you for making time for me during such a busy time today.
I'm sorry, I can't come today.
Thank you for making time for me today.
Sorry for being late today.
Thank you very much for your hospitality today.
Thanks for giving me some of your time today.
I regret that I can't come today.
I regret that I can't come today.
Thank you all for coming today.
Unfortunately, I don't have time today.