Am I being unreasonable?

I consider myself a fairly reasonable person. I try to be fair and consider both sides (in most situations :). As many of you know, my oldest daughter, Shalyn is from my first marriage. Her father lives in another state and has visitation rights. He has her for three weeks during the summer and the second weekend of every month (Fri-Sun). We also rotate all the major holidays (Easter, Thanksgiving, and Christmas). Shalyn just got home last Friday from a two week visit with him (she spent a week in June with him too.)

A few days ago I got an email from X asking for extra days in August (flying out on a Wed instead of a Fri) and to have her over Labor day weekend. For the Aug visit, I told him no because she has piano camp all that week and Labor Day was a no too because my parents will be in town. So then I get another email asking if she can stay in Aug until Tues.

I feel really frustrated with this because this year I have allowed Shalyn to spend extra time with him on a few occasions. She missed an entire week of school to go on a cruise with him in Feb, and she missed a few days of school in May when she went out to see him. Not to mention that when she was out there for the last two weeks, he couldn't be bothered to take time off of work to spend time with her. She spent her days either visiting other relatives of his or sitting alone in his apartment.

I don't like being inflexible and insisting we stick to exactly to the court order, but I feel like anytime I give him any leeway he takes advantage of it and demands more and more. The idiom "you give an inch and he takes a mile" definitely fits with our situation. So I responded to the last email by saying, "I'm not trying to be unreasonable, but you've already had your summer visit with her." So today there is the whiniest email in my inbox trying to guilt me into giving into him. Sorry, I'm not going to do that. I feel like I've been more than fair.