how to create a loading page for flash social game?

hi,

first i am not asking about the page design, i am asking about coding, let's start

before the game start it's take some time to load, depending on that it will be the first page the player will see always, the back ground will be any thing and there's the bar that show how much loaded and how much will load like(20%)

simply i don't know any thing about how i connect that bar with loading data, any body know any thing about that?