i'm a student, needed some guidance/help with my project..

i need to apply changes to the desktop after changing the wallpaper from the file /opt/ kde/share/config/kdesktorc (which we generally do by pressing the APPLY button), but i need to do this through the command line and not through using the APPLY button... the one solution seems to be to logout, and login again, which automatically refreshes the screen, but i need this to happen immediately, basically exactly like the functionality of the APPLY button itself.. please help me out!