integration filebrowser with .net

I am trying to configure a custum UserFiles Directory (the one where you upload your media to) and cannot find a way to do this. It is stated that this is configureable in the wiki, but I cannot find the right entries on the expected places.

I tried to add
[ Category("Configurations") ]
public string UserFilesPath {
get {
return this.Config["UserFilesPath"];
}
set {
this.Config["UserFilesPath"] = value;
}
}

to FCKeditor.cs, but it does nothing.

This is quite urgent, so any help is gladly appreciated!

Jan