How to validate input file that have been added dynamically using jquery

I create a form that contains a button to add a group of input fields dynamically one of them is an input file "I want to validate its size before uploading"

jQuery:

    $('.formLayout .moreSubjects').click(function(){
    var box_html = $('<div id="more-subjects"><br><label>Subject</label><input type="text" name="subject['+numberIncrC+']" dir="rtl" class="subject_list"><br><label>Attachment</label><input type="file"  name="attachment['+numberIncrC+']" id="subjectToUpload'+numberIncrC+'" class="att_list"><label id="lbSize'+numberIncrC+'"></label><br><label>Status</label><select name="status['+numberIncrC+']" class="status_list"><option value="none">&nbsp;</option><option value="approved">Approved</option><option value="rejected">Rejected</option><option value="underStudy">Under study</option></select><br><label>Date</label><input type="date" name="deadline['+numberIncrC+']"><br><label>Comments</label><textarea rows="4" cols="50" name="comments['+numberIncrC+']" dir="rtl"></textarea><button class="remove-box">Delete</button></div>');

    box_html.hide();
    $('.more-subjects').append(box_html);
    box_html.fadeIn('slow');
    $('.subject_list').each(function () {
    $(this).rules("add", {
        required: true,
        messages: {
            required: ".."
        }
    });

});
$('.att_list').each(function () {
$(this).rules("add", {
        required: true,
        accept: "doc|docx|pdf",
        messages: {
            required: "..",
            accept: "..",
        }});

$('select.status_list').each(function () {
$(this).rules('add', {
checkStatus: true
});

jQuery.validator.addMethod('checkStatus', function (value) {
    return (value != 'none');
}, ".."); });
});
    numberIncrC++;
    return false;
});

File size method:

jQuery.validator.addMethod('checkSize', function ()
{
    if(!$("#subjectToUpload"+numberIncrC).val() == '')
    {
                var iSize = ($("#subjectToUpload"+numberIncrC)[0].files[0].size / 1024); 
                if (iSize / 1024 > 1) 
                { 
                    if (((iSize / 1024) / 1024) > 1) 
                        { 
                            iSize = (Math.round(((iSize / 1024) / 1024) * 100) / 100);
                            $("#lbSize"+numberIncrC).html( iSize + " GB"); 
                        }
                    else
                        { 
                            iSize = (Math.round((iSize / 1024) * 100) / 100)
                            $("#lbSize"+numberIncrC).html( iSize + " MB"); 
                        } 
                } 
                else 
                {
                    iSize = (Math.round(iSize * 100) / 100)
                    $("#lbSize"+numberIncrC).html( iSize  + " KB"); 
                }   
        return (iSize<4294967295 ); // 4GB is 4,294,967,295 bytes
        }
        return true;
}, "..");

Now where should I call this method to check the size of each file ?