function getElement(psID) { 
  if(document.all) {return document.all[psID];}
  else{return document.getElementById(psID);}
} 

function buildActivity() {
  var objActivityCategory=getElement('ActivityCategory');
  var objActivity=getElement('Activity');
  var arrList=new Array();
  
  objActivity.options.length=0;
  var j=0;
  if(objActivityCategory.value==0){objActivity.options[j]=new Option('(all activities)', 0);}
  else{objActivity.options[j] = new Option('(all ' + objActivityCategory[objActivityCategory.selectedIndex].innerHTML +  ')', 0);}
  for (var i=0; i<activityOptions.length; i++) {
    var opt=activityOptions[i].split(';');
    if(opt[0]==objActivityCategory.value){
      j++;
      objActivity.options[j] = new Option(opt[2], opt[1]);
    }
  }
  objActivity.disabled = true;
  if(j>1) { 
    objActivity.disabled = false; 
  }
}