@sand15 thanks for helping me. Now i understood how to do it, but i'm having other problems. I can't change the value of MathMLViewers in the new window. I tried a lot of ways to do it, but doesn't work or appears this error message:. I can't work with two windows opened at the same time, because if i try to get some value inserted in one TextField at the first window and show it on a MathMLViewer at the second one, it just doesn't work. Do you know how i can do it?

Well, i succeed doing a button that opens another window, but i still don't knowing how to do an interface with N TextFields, somebody can help me?