F.A.O Mr Pom, or anyone else Pom like

I’ve just completed the sliding menu that Pom did a while ago I guess. I want to tailor the menu to suit need and I need to crack the brain behind the code. Specifically Pom used:

[COLOR=royalblue]On button 1[/COLOR]

on (press) {
_root.xnew = _root.mask2._x+(4-1)*100/2;
}

to determine the direction and the final resting place of menu one

Ok so *100- this must be the width of the menu but /2 ??

(4-1)-there are four menus so…

I want to use menus of 700x100 x3

I have attached a .fla

Is there anyone that can help with the code. OK so I understand it but I need to change some values so a little extra insight would be great.

Any ideas??