Well, if you have CS:S, you already have an HL2.exe. (Love the icon for it btw
) I'm not sure that CreateInterface is actually exported by HL2. It's certainly used in HL2.exe somewhere. But as far as I could tell it was exported from the server and client DLLs. Anyways it's pretty easy to find information like that, if you have a program like I do. :-P But a nice hex editor would work too, heh.