function updateForm() {

  var myVal=form1.elements['participants'].value;

  var siblings=document.getElementById('siblings');
  if (siblings){
    if (myVal>1){
      siblings.style.display='block';
    } else {
      siblings.style.display='none';
    }
  }

  updateCostSummary();

  var arr;
  switch (myVal){
    case '1': arr = new Array('1','0','0','0','0','0','0'); break;
    case '2': arr = new Array('1','1','0','0','0','0','0'); break;
    case '3': arr = new Array('1','1','1','0','0','0','0'); break;
    case '4': arr = new Array('1','1','1','1','0','0','0'); break;
    case '5': arr = new Array('1','1','1','1','1','0','0'); break;
    case '6': arr = new Array('1','1','1','1','1','1','0'); break;
    case '7': arr = new Array('1','1','1','1','1','1','1'); break;
    default: arr = new Array('1','0','0','0','0','0','0'); break;
  }
  setVisibilities(arr);
}
function setVisibilities(arr){
  for (var i=0; i<arr.length; i++){
    var div=document.getElementById('participant'+(i+1));
    if (div){
      if (arr[i]==1){
        div.style.display='block';
        div.style.visibility='visible';
      } else {
        div.style.display='none';
        div.style.visibility='hidden';
      }
    }
  }
}
function updateCostSummary(){
  var participants=form1.elements['participants'].value;
  var siblings_radio, costValue;
  var costsummary=document.getElementById('costsummary');
  if ((form1.elements['siblings_radio'][0].checked) && (participants>1)) {
    //siblings_radio=true;
    costValue=47+(participants-1)*30;
    costsummary.innerHTML='<strong>Cost Summary</strong>: (1 x $47) + ('+(participants-1)+' x $30) = $'+costValue;
  } else if (participants<7){
    //siblings_radio=false;
    costValue=participants*47;
    costsummary.innerHTML='<strong>Cost Summary</strong>: '+participants+' x $47 = $'+costValue;
  } else {
    costValue=(participants-1)*47;
    costsummary.innerHTML='<strong>Cost Summary</strong>: 6 x $47 = $'+costValue+' (7th is free!)';
  }
  form1.elements['cost_total'].value = costValue;
}