The best way to explain this is with this watered-down example:
public class BaseClass
public function getEncoded(Arg1 as string, Arg2 as string) as string
return BCODE + ";" + Arg1 + ";" + Arg2
public class Class1
public const BCODE as string = "AABBCC"
How do I do this? (the example above gives an error, since BCODE doesn't exist in the base class)