He's doing it again

I need some advice from you guys...

My exNH has a habit of forgetting when he is to take my son and plans vacations without even telling me he'll be out of town. Because I'm self employed, I revolve my work schedule (and my social activities) around when he is supposed to take him. The visitation/custody is a little complicated. He is a firefighter so he works four days and has four days off.
During the school year, I have my son primarily and the N is to take him one evening a week for dinner and two weekends a month based on his work shift..when he has weekends off.
Now. During the summer when my son is out of school, his dad is to have him for his four days off and then I get him for the four days he is working.
Monday is to be the first of HIS four days to take our son now that he's out of school....but alas, conveniently, he tells me last week that he will be out of town.
I finally got a job that I've been working on, and my 17 yo son is helping me with it. (17yo lives with dad) I planned it for that time knowing that my younger son would be with his dad and I wouldn't have to worry about getting someone to watch him. (There's no one anyway that would do that for me and I don't have any daycare established.)
Today I find out that exNH is STILL planning on going out of town on Monday and has planned to leave my younger son home WITH THE 17yo at his house while he is gone!!! So, the 17yo won't be available to help me and I really needed his help.

My lawyer tells me I have really no recourse with this stuff. As long as he's paying support the courts could care less if he takes him when he's supposed to or not.
However, it effects my ability to work when he does this.
I want to stick it to him so bad, he's been screwing me over this way for two years! ANY suggestions? This has got to stop...or I need to have a little bit more control over my own life!
Thanks!
~Denise~