JQuery :: Saving Values From A Multi Select List?

Im using a plugin called select chain and modified it a bit. Right now im trying to pass only selected values of a multi select list through ajax. The following function does a bit more but im concerned with the part that says cust_val: customer.val().join(",") This should return only selected values. This is what happens if i put it in an alert(). however when i check firebug to see what was posted it shows the entire list. I've tried alternatives like option:selected.... they all work for aler() .. the info passed through ajax shows the entire list.

customer.selectChain({
target: market,
url: callback_url,
type: "POST",
data: { ajax: true, multsel: market_selects, cust_val:
customer.val().join(",") }
}).trigger('change');