Trigger Script On Checkbox Select

Hi, All. I'm new to Gravity Forms and love it. Have an issue I've been researching for a couple hours with no luck, so any help would be appreciated.

I'm trying to trigger a count of checkboxes selected on the first page of a multipage form. Here's my code:`

<div id="counter"></div>
<script>
function countChecked() {
var n = $("input:checked").length;
$("div#counter").text(n + (n <= 1 ? " is" : " are") + " checked!");
}
countChecked();
$(":checkbox").click(countChecked);
</script>`

It works when I throw up a sample form with checkboxes above the gravity form, but when I remove the sample form so that only inputs from GF should trigger it, nothing happens.

Any help would be appreciated.

Thanks,

Pierre