I went to the Internet (of course) for help and found a few tips. The first one I found said to put a stress ball between your knees, then when you go to cross your legs, you will think about the stress ball being there, and not do it. I remembered the stress ball I got when I started my new job, stuck in the bottom drawer of my desk.
I am aware of the irony of me taking a picture of the ball propped up on my crossed legs, but it's the only way I could figure out to get a good shot without my boss noticing I was taking pictures!
Success! I didn't cross my legs for several hours. My muscles started to get tired of holding it between my knees after about an hour (not only a re-training tool, but a leg workout as well!) so I moved it up a bit, and it still worked just as well! The only problem was standing up. It's hard to look graceful when you're pulling a stress ball from between your knees every time you need a drink of water... But if you work in a less shared space than I do, I highly recommend it! In fact, I even recommend it if you do share a space. I care much more about my hips than what my co workers think of me!