anchor.diff:              executeUpdateDetails(input)
           })
       })
  +
  +    $$('.counter').each(function(input) {
  +        input.observe("click", function() {
  +            var spanElt = input.getElementsByClassName('marker')[0].innerHTML.toString()
  +            var inputElt = input.select("input")[0]
  +            var spanValue = spanElt.replace(/\s/g, "")
  +            if (spanValue.empty()) {
  +                executePlannedActivityAdd(inputElt.id, null)
  +                input.select(".marker")[0].innerHTML = 'X';
  +            }
  +        });
  +
  +        input.observe('mouseover', function(){
  +            input.addClassName('hover')
  +        });
  +
  +        input.observe('mouseout', function(){
  +            input.removeClassName('hover')
  +        });
  +    })
  +
   }
   
   function updateAddActivityButton() {
  
positive.code: .palette div#delete-drop.hover {
      background-color: #f99;
      cursor: pointer;
  }
  
  .palette .tip {
  
negative.code:                     accept: ['marker', 'new-marker'],
                      hoverclass: 'hover',
                      onDrop: moveMarker })
                      registerHoverTip(item, "Click the grid cell to add an activity for all subjects")
              }
              );
  
  