checkbox coordinates

Im trying to display a floating layer that could move beside a series of checkboxes. I can move the layer and change the text with no problem but I dont know what the coordinates are to move it to.

Im using this:
<A HREF="#" onClick="
document.all('Divfloat').innerHTML = '$desc';
Divfloat.style.visibility='visible';
Divfloat.style.left='200';" >...</A>

that sets the properties of the layer but I cant figure out how to get the coordinate for the top of a checkbox that it supposed to be near.

I was thinking something like this but I cant get it to work
Divfloat.style.top=document.All.item("checkbox1").offsettop;

Does anyone know how to get the coordinate of an object like a checkbox so I can use it to make something move beside it?

Code:

---

function getTopCoords(id) {
    var obj = document.getElementById(id);
    var posY = obj.offsetTop + obj.offsetHeight;
    while (obj.offsetParent) {
        obj = obj.offsetParent;
        posY += obj.offsetTop;
    }
    return posY;
}

---

where id is the id of the checkbox