//   Which class offering 

function checkOnlyOneWhichClass(num)
{
for (j = 0; j < 4; j++)
   {
      if (eval("document.courseApplication.which_class[" + j + "].checked") == true)
         {
            document.courseApplication.which_class[j].checked = false;
            if (j == num)
               {
                  document.courseApplication.which_class[j].checked = true;
               }
         }
   }
}