function changeNoOfParticipants(obj) {
    noOfParticipants = obj.options[obj.selectedIndex].value;
    hideAllParticipantRows();
    for (i=1 ; i <= parseInt(noOfParticipants) ; i++) {
        document.getElementById('participant-row-' + i).style.display = '';
    }
}

function hideAllParticipantRows() {
    participantRowTags = document.getElementById('participant-rows').childNodes;
    for (i=0 ; i < participantRowTags.length ; i++) {
        if (participantRowTags[i].nodeType == 1) {
            participantRowTags[i].style.display = 'none';
        }
    }
}