According to this JS code, I can limit the number of checked boxes in a Checkbox field.

<script type="text/javascript">



jQuery(document).ready(function($){



var limit = 3;// Change 3 to your limit



$('input[name="item_meta[364][]"]').change(function(){



var checkbox_num = $("input[name='item_meta[364][]']:checked").length;



if ( checkbox_num > limit ) {


    this.checked = false;


}



});



});



</script>

And it works well, even there is a built-in mode to accomplish this.
But it does not work however in the checkboxes mode of a Dynamic field. I tried even changing "input" by "select", but it keeps failing. Unfortunately, checkboxes mode of Dyn fields has not a Limit selection option.
What's the secret here? Not referencing it correctly?

(EDIT: I tried to change this question to Code Help editing it but I couldn't.)