Disable checkbox on dynamically created elements jQuery

I am trying to disable checkbox elements on GPA Calculator App using jQuery

The checkbox is created dynamically when adding a new course to indicate if the student has repeated the course in order to fill his previous grade on it:

    if(hourSum < 21){
      $("<div class='course'>"
                       + "<div class='tdnum'>"
                       + "<span class='subNum' id='subNum" + i + "'>" + i + " </span>"
                       + "</div>"
                       + "<div class='tdgrade'>"
                       + "<span class='requiredMsg' id='markReq" + i + "'>*</span>"
                       + "<input type='number' class='mark'>"
                       + "<span class='errorMessage' id='markError" + i + "'>* between 35 - 100</span>"
                       + "</div>"
                       + "<div class='tdhour'>"
                       + "<span class='requiredMsg' id='shourReq" + i + "'>*</span>"
                       + "<input type='number' class='shour'>"
                       + "<span class='errorMessage' id='shourError" + i + "'>* between 1 - 3</span>"
                       + "</div>"
                       + "<div class='tdrep'>"
                       + "<input id='subState" + i + "' class='repSub' type='checkbox'>"
                       + "</div>"
                       + "<div class='tdpgrade'>"
                       + "<input type='number' class='rmark' id='rmark" + i + "' disabled>"
                       + "<span class='errorMessage' id='rmarkError" + i + "'>* between 35 - 100</span>"
                       + "</div>"
                       + "<div class='tddelete'>"
                       + "<span class='remove'><img src='img/delete.png'></span>"
                       + "</div>"
                   + "</div>").appendTo(".ctable").hide().fadeIn(300); // add fade effect on adding elements          
             i++;
}

I need to disable this checkbox of class .repSub when number of passed hours = 0 and overall average = 0

"<input id='subState" + i + "' class='repSub' type='checkbox'>"

I tried this method:

 $(".repSub").prop("disabled", true);

also I tried :

$('.repSub').attr("disabled", 'disabled');

but both methods aren't working on dynamically created checkbox

is there any worked solution for this problem ?