for server commands, use
function serverCommandskychange(%client, %skybox)
{
<code>
}
%client is the client calling the method, you should probably check if they're admin if you want to limit the command to admins only
%skybox will be the user input for which skybox to change it to
not sure what the skybox functions are, but you could try running a trace and changing the skybox with the GUI, it may tell you which functions to call