Modpack help

Heyu, If anyone can help me figure this out, that would be great. What I want to know is how can i create a modpack launcher like tekkit or feed the beast? I looked all over google and couldnt find a good explanation how. Also i know like nothing of the code, so I dont know how to "Just mofify the code" And i dont even know where to find it. it would be great if someone created a program that automaticly has a launcher like that.