Updating flash 4 actionscript to flash 8!

Hi guys, I’ve made a pretty stupid error and was wondering if someone with a bit more know-how could offer me some help…

I’ve been working on a looping paralax scroller, of which I took the basic actionscript from an open source .fla file, figured out what all the code did and got it working how I wanted, and then realised that the publish settings were set at Flash 4, and when I changed that to Flash 8, it kills the movie, and nothing works, so im begging for an expert to give me an opinion on how I can get it up and running in Flash 8, below is the code for examination and I’ll attach the .fla incase anyones interested enough in having a look

Frame 1:

mover = getProperty("scrollingobject", _x);

Frame 20:

mouseh = getProperty("/tracker", _x);
mousev = getProperty("/tracker", _y);
if (Number(mousev)>200 and Number(mousev)<280) {
    movevalue = (Number(movevalue*9)+Number(((mouseh-350)/20)))/10;

Frame 21:

mover = Number(mover)+Number(movevalue);
if (Number(mover)>2800) {
    mover = -700;
if (Number(mover)<-2800) {
    mover = 701;

setProperty("/scrollingobject", _x, mover);


**source file: **http://www.subman.co.uk/fla/scroller4.fla

I really would be extremely grateful for any help anyone could give me on this one as Im pulling my hair out over it at the moment!

thanks in advance!