function prepareCheckBoxes(groupName, limit){
  if (!document.getElementsByTagName('input')){
    return;
  }
  var formItems = document.getElementsByTagName('input');
  var checkGroup = new Array(); 
  for (var i=0; i<formItems.length; i++){
    if (formItems[i].getAttribute('name') == groupName){
      checkGroup.push(i)
    }
  }
  for (var i=0; i<checkGroup.length; i++){
    formItems[checkGroup[i]].onclick = function(){
      var count = 0; 
      for (var j=0; j<checkGroup.length; j++) {
        if (formItems[checkGroup[j]].checked){
          count++;
        }
      } 
      if (count > limit){
        alert("Please choose a maximum of "+limit+" selections.")
      this.checked=false
      }
   }
  }	
}

window.onload = function(){
  prepareCheckBoxes('Reason-For-Choosing-Focal-Point[]', 3);
  prepareCheckBoxes('Reason-for-Purchasing[]', 3);
  prepareCheckBoxes('Reason-for-Purchasing-Outside-Focal-Point[]', 3);
};