Tell him "sorry, already made plans on the 24th." and make him solve the problem!

In your case, staying "cold" in tone is best, I think. It is 180 of you normally, right, and he is acting like an $%$#* so it is best.

I say wait until after Christmas, if you can afford it, because it will prolong the process a bit and hopefully he will have some emotional reaction to this year's Christmas. Just a thought.

me,34
exH,34
S,16 months
S:3/31/09-left for OW
started DBing 10/09
d final: sometime 10/10
current:
http://www.divorcebusting.com/forums/ubbthreads.php?ubb=showflat&Number=2022856&page=1
met in 2004