You are right. It is a really big program. But I create a Dock Palette with C#.net. I add some buttons on it. I can load different lisp program by click each button. When I click one button, the lisp program will be running in the command. If you click another button at this time, the new lisp program won't be loaded because of the first lisp program is not finished. So when I click the second buuton, I want to stop the first lisp program before I load the second lisp program. Is it poosible in C#.net?