Default Value In Select List

I'm trying to figure out how to preselect a country in a form, I have this so far:
--------------------
<form name=order>
<select name=country>
<option value="aaa">aaa</option>
<option value="aaa">bbb</option>
<option value="bbb">ccc</option>
</select>
</form>
<script>
document.order.country.selectedIndex=1;
</script>
---------------------

But I would like to be able to preselect a country based on the option value.
Something like (this doesn't work obviously):

document.order.country.selected.option='bbb'


The default value for the country will be supplied by a previous form, so it changes depending on what has been selected in the previous form.