using javascript to change css cursor

[android1]

Hi,
I am trying to alter some css using external javascript. I have 48 thumbnails on a page which bring up a pointer cursor onmouseover. The thumbnails have div ids of 'thumb_2_2' up to 'thumb_2_49' and a css class of 'thumb2'. I need to alter the cursor so that in certain situations the pointer doesn't show.
This is the css :

div.thumb2 {cursor:pointer;}

I have tried altering the css class like this :

window.thumb2.style.cursor="default";

and have also tried altering the individual divs like this :

for(var i=2; i<=49;i++){
document.getElementById['thumb_2_'+i].style.cursor="default";
}

and also like this :

for(var i=2; i<=49; i++){
document.images['thumb_2_'+i].style.cursor="default";
}

but nothing seems to work.

I would be really grateful if anyone could help. Thanks.