javascript timing

Hello,
I realize from reading the docs and this forum that javascript is not for timing-critical tasks. However, I want to use for something where even 100 ms. off won't make a difference. In particular, I want to have a series of processes which randomly update their internal timing. However, when I attempt to measure what the result is (using timer), I'm getting stuff that's pretty far off. It's entirely possible that I'm doing something stupid, or not grasping something. Anyway, the javascript (which wants to be in a file named "debug.js") and the patch follow. I was expecting the number boxes to display approximately the same numbers (which they don't most of the time). thanks!, Michael

inlets = 1;
outlets = 1;

var rOffset = 3000;
var rRange = 2000;

var vcTsk = new Task(vcDo,this);
vcTsk.interval = 4000;

function vcDo()
{
outlet(0,vcTsk.interval);    
vcTsk.interval = Math.round(Math.random()*rRange) + rOffset;
}

function msg_int(a){

    if (a == 1){
        vcTsk.repeat();
    }
    if (a == 0){
        vcTsk.cancel();
    }
}