Roller Coaster

I guess this is what they mean. I thought we had everything pretty much worked out, I am moving thursday and Friday, and was moving my son in with me full time, and my daughter 1/2 time.  Today the stbx calls and says she won't allow my son to move, that until there is an agreement in place she will not allow him to leave.  I have a call in to my atty now, but won't talk to him until tomorrow.  I hate this last minute stuff.  My son wants to move, I want him to, but she is being adamant about this.  It will all work out, but if I let myself, I could get really angry right now.  Instead, I'm somehow staying calm.