How to get value of select box for button_to?

Hi,
I have a select box with the following options:
<select id="flight_destination" name="flight[destination]">
<option value="">Destination</option>
<optgroup label="Australia">
<option value="OOL">GoldCoast</option>
<option value="MEL">Melbourne</option>
</optgroup>
</select>

How do I get the value of the select box into the button_to?
<%= button_to "Search", {:controller =>
"ticket", :action=>"search", :depart=>"KUL", :arrival=>???} %>