Need help with checkbox dependencies

Need help with checkbox dependencies

Hi,
I have 3 checkboxes "#MKDPT", "#NDQL1" and "#NDQL2". If "#NDQL2" is checked, I need to loop through and make sure "#NDQL1"  is checked if it is unchecked, check it. Then check if "#MKDPT" is checked. If "#MKDPT" is unchecked it needs to be checked as well. Basically, if "#NDQL2" is checked the other two must be as well. Im having trouble checking the value to see if a checkbox is unchecked. I  have tried several functions but to no avail, not sure which one to attach the click function or if I need to use a .change(function(evt) {}


$(document).ready(function() {
     $("#NDQL2").change(function(evt) {
        if($("#NDQL2").is(":checked")) {
            $("#NDQL1").val() !== null;   
        }
    });
});
</script>

Also, how do you check if a checkboxes value is "not checked or false"?
Thanks
Kane Leins