To do what you're thinking you'll need a scripting engine like Lua. However, you'd be better coding your game engine to handle "levels" and make it a self contained file which describe how to do everything needed for that level.
Kind of like how the unreal engine works. Each UNR (or whatever it's called now) is a self contained archive containing level geometry, textures, sounds, scripts, UIs all in the same file. It's the game engine which takes all that and displays it on screen or whatever.
In my game engine, everything is based on XML, so at the start of my code, I have a function which automatically opens default.xml. This xml file will contain the main menu interface, how the 3d scene for the menuscreen will look like, what music to play, and what each menu option will do. If I click on the "Play Game" button, what the engine is actually doing is calling a few pre written functions to remove the existing level/UI, then open another xml which contains everything needed for level 1 of my game.
I live for video games! (And beers, and football, and cars!)
See what I live for here: [url]http:\\www.TeamDefiant.co.uk[/url]