Here is a quick example for adding and removing options from a single select list. Hope it helps since I've spent some time figuring it out. :)

Add option to select list in FBML with appendChild()

function addOption(id, value, text) {
    var select = document.getElementById(id);
    var option = document.createElement('option');
    option.setValue(value).setTextValue(text);
    select.appendChild(option);
}

Remove option from select list in FBML with removeChild()

var choiceList = document.getElementById('someID');

var count = choiceList.getOptions().length - 1;
var node = choiceList.getOptions()[count];
choiceList.removeChild(node);

Clear all options at once

function clearAllOptions(id) {
    document.getElementById(id).setTextValue('');
}

December 18, 2009     

thx

Just thanx for the job. I'm new in FBJS and thx to your work I avoid to spend a lot of time
Cdric | 82.241.105.233