Advancing through scene elements?

Hello, I want to have the player click to advance some elements in my scene, but how do I have the functions load one after the other? In my bowling game, the player advances the game flow works like this

:players use arrows the determine the balls starting horizontal position, click to advance :The ball rotates back and forth to determine its angle, click to stop it and advance :A rebounding meter appears to determine the balls velocity, click to set it and throw the ball.

How can I call the different GUI elements and make sure things come up in the correct order?

Try something like this (untested example code):

int state = 0;

void OnGUI()
  switch(state) {
  case 0:
  case 1:
  case 2:

in the functions you should then check for input and if the user is done and do state++.