CUSTOM MENU [HELP NEEDED]

Hello, I'm using rpgmaker 2003 and I would really like to add a custom menu that would let you choose a job.
I have a knowledge of switches and variables, and I also have the right tools to edit pictures, sprites and different stuff. The only thing I need is a simple tutorial that would teach me step by step, how to create a custom job system. I tried the tutorial on "rpg revolution", but that didn't help much. So please, if you would help me, that would be awesome!