tri-state Checkbox style not being implemented

tri-state Checkbox style not being implemented

I am trying to implement a Tri-state Checkbox i am able to load its
Intermediate State Image(which i can see using fire bug), but i am unable
to kinda Overwrite the original checkbox with the Intermediate state image
jQuery('[id^="status-"]').click(function(event) {
var childtTrID = $(this).parents('tr').attr('data-tt-parent-id');
$('#tblAllocationList').find('tr').each(function() {
if (childtTrID == $(this).prop('id')) {
$(this).find('td
input:first').addClass('intermediateCheckedCss');
}
});
});
If you need any further code/info plz tell me in comments