Preloader BATTLE

I am totally lost I have been battling this for hours… so here goes:

I have a preloader script which specifically loads into one of my 6 holders in the root, holder4.

It works fine for holder 4, but I also have stuff loading into the others at anygiven time, how do I tell script it to count the SUM of all the bytes about to be loaded into all the relevant holders rather than just holder 4???

here is the script as it is now, which is on my root:

loaderbar._visible=false
loadtext._visible=false

function loader()
{loaderbar._visible=true
loadtext._visible=true
_root.loadertxt._visible=true
_root.onEnterFrame=function()
{

total=_root.holder4.getBytesTotal()
loaded=_root.holder4.getBytesLoaded()
_root.percen=Math.floor((loaded/total)*100)+"%";

if((loaded/total)>=1)
{
loaderbar._visible=false
loadtext._visible=false;
delete _root.onEnterFrame;
_root.loadertxt._visible=false
}
_root.loaderbar._xscale=(loaded/total)*100

}

}

PLEASE HELP!!