Simple javascript to ensure that checkboxes act in an incremental fashion. If checkbox 5 is clicked, then ALL checkboxes up to 5 will be checked, if checkbox 2 is unchecked, then all checkboxes after 2 will be unchecked as well.

incremental_checkboxes.js

<script type="text/javascript">
	/* Javascript to force incremental changes 
	 * If checkbox 1,2, 5 are checked then all
	 * migrations 1,2,3,4,5 should be applied.
	 * If checkbox 3 is unchecked, all checkboxes
	 * after 3 should be unchecked as well.
	*/
	var inputs = document.getElementsByName("migrations[]");
	for (var i = inputs.length - 1; i >= 0; i--) {
		inputs[i].onclick = function(evt){
			var parentTr = this.parentNode.parentNode.parentNode;
			if( this.checked ){
				/* Find and set the previous children to true*/
				while(parentTr){
					parentTr.firstChild.firstChild.firstChild.checked = true;
					parentTr = parentTr.previousElementSibling;
				}
			}else{
				/* Find and set the future children to false */
				while(parentTr){
					parentTr.firstChild.firstChild.firstChild.checked = false;
					parentTr = parentTr.nextElementSibling;
				}
			}
		}
	};
</script>