//Concatenates selected category IDs into a comma-separated list
function getSelectedCatIds(formName,checkboxName){

  var catcount = document[formName][checkboxName].length;
  var catids = new Array();
  var catindex = 0;

  for(i = 0; i < catcount; i++){
     if(document[formName][checkboxName][i].checked){
     catids[catindex++] = document[formName][checkboxName][i].value;
     }

  }

  return catids.toString();

}