I try this, but now I have error
Wrong usage/parameters for this command!
Read the documentation!
File: Dialogs.hws (current line: 1150 - In function: ChangeDisplayMode)
I see you're using RapaGUI. Going full screen isn't supported with RapaGUI. This is only supported with Hollywood's default display adapter or plugins like GL Galore and RebelSDL. Going full screen in a GUI application doesn't really make sense.
Maybe it could be handy, I don't know, but if you set the screen size in the xml declaration you can have a window at the full size of the hosted screen using this syntax: