Dynamic multi-selects? please help!

System

Is it possible to have a dynamic multiselect...i.e. if a top level multiselect has options 1-10 and a user picks 1, 3, 5, then certain multiselects below would ONLY have items 1,3,5 in them? any examples would be appreciated.

i can get it to work when a user only selects 1 option at a time, but not when multiple are selected at one. ive been playing around with arrays but have had no luck.

here is what i have so far:

IWEventRegistry.addItemHandler("/audience_category", "onItemChange", deliveryItems);

function deliveryItems(item) {

var aud_cat = IWDatacapture.getItem("/audience_category");
var aud_cat_options = aud_cat.getOptions();
var aud_cat_SelectionIndex = aud_cat.getValue();

var cat_code = aud_cat_options[aud_cat_SelectionIndex].value;
var label = aud_cat_options[aud_cat_SelectionIndex].text;

var item = IWDatacapture.getItem("/test");
var newOption = new Option(label, cat_code, false, false);
item.addOption(newOption);

IWDatacapture.redraw();

}