I want to hide the upload button from the image upload cck filed at the time of node creation.
To achieve this goal you can apply javascript :

$(document).ready(function() {

$('#<---form id-->').attr('hidden', true);

});

Write the above code in a block and enable this block on that page you found upload button. Like "node/add/

I got success by implementing above .

(You may also remove that node form open in lightbox simply you have to write the above code in the lightbox template file that you have created to the node form.)

Cheers!