I think I understand. I'm pretty sure Jason released a library with methods to inject managed assemblies into a process. Try writing an assembly(class library, dll) that, once loaded and running in the target process, uses reflection to find all objects of type Label. In C# it would be like "if (object yadablahblah is Label) { (Label)yadablahblah.Text = "What the tits?"}
If I'm understanding this correctly, it really isn't too hard. You need to understand basic polymorphism and learn to use reflection. If the program you're injecting is your own, then there are probably a hundred or so better ways to do this.